HKDSE Physics Elective C Wave Motion by topic - HKEAA

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AL CE DSE. BY-TOPIC PAST PAPER f .c: ·- 0, U ,U Ln I , 'i lO DSE Physics - Section C : M.C. PC-WAl-M/01 DSE Physics - Section C : M.C. PC-WAl-M/02 WAl : Wave Propagation WAl : Wave Propagation t� Part A : HKCE examination questions 4. < HKCE 1991 Paper ll- 23 > -----3>- Direction ofwave 1. <HKCE 1983 Paper n- 26 > p Vibrator A vibrator of frequency 5 Hz generates waves on a string. The above diagram shows the shape ofthe string at the instant -------- Q ----- when the vibrator has made one complete VJ.bration. Which of the following best shows the wavefon:n 0.1 slater? A. (vD­ - R B. A transVerse wave is travelling steadily from left to right through a series of particles. At a certain instant the wave form is as shown in the figure. Which of the following statements about the particles is/are correct? (1) Particle P is IIlOVmg down. (2) Particle Q is moving up. rJ\y- AAr (3) Particle R is momentarily at resL C. A. (I) only B. (2) only C. (1) & (2) only D. (2) & (3) only D. 2. <HKCE 1987Paper 11-11 > � t = 0.000 s 5. < HK.CE 1991 Paper ll- 21 > �---­ p ---➔ Direction of wave Q t = 0.025 s �----· The above diagram shows a water wave travelling to the right. Which ofthe following statements is/are true? The above figures show a wave in the same section of string at two different instants, What is the greatest possible pe riod of (1) PQ is equal to the wavelength. the wave? (2) PR represents the amplitude. A. 0.025 s (3) The particle at P will move to S after a quarter of a period. B. 0.050s A. (1) only c. 0.100 s B. (3) only D. 0.200 s C. (1) & (2) only D. (2) & (3) only �-� 3. < HKCE 1988 Paper Il - 12 > 6. < HK.CE 1992 Paper II- 22 > ------'----------�---------------- The above diagram shows a progressive transVerse wave at a certain instant when traVelling from left to right. 'Which of the following correctly shows the direction ofrootion of the particles at P, Q andR? A water wave travels towards the right. The above diagram shows the waveform at a certain instant. Which of the following p Q R statements is/are true? (1) Particle P is moving downwards. A. ➔ ➔ ➔ (2) Particle Q is moving upwards. B. .j. -1- -1- (3) Particle R is momentarily at rest. A. (1) only C. -1- t -1- B. (3) only C. (1) & (2) only D. t -1- t D. (2) & (3) only DSE Physics - Section C : M.C. PC-WAl-M/03 DSE Physics - Section C : MC. PC-WAl-M/04 WAl : Wave Propagation WAl: Wave Propagation 7. <BKCE1993Paperll-22> 10. < HKCE 1999 Paper II- 20 > ---➔ Direction of wave A cork in the water vibrates up and down 4 times in 2 s when a wave passes through it The distance between r.vo successive I£:\V _____D,__ crests ofthe wave is IO cm. Find the speed ofthe water wave. A. 0.05mir1 Vibrator P Q B. 0.1 ms- 1 C. 0.2 ms- 1 D. 0.4ml>1 A viorator generates a travelling wave on a string. The above diagnun shows the shape ofthe string at a certain instant Which ofthefollowing shows the shape of the string betweenPQ after a quarter ofa period? R 11. < BKCE 1999 Paper II - 21 > A (\} The diagram shows a transverse wave travelling along a string. p Q At the instant shown, particle Pis moving upwards. Which ofthe following statements is incorrect ? A. The wave is travelling towards the left. B. Particles P and Q VJ.lirate with the same :frequency. c. D. C. Particle Q is moving downwards at this :instant. D. Particle R is at rest at this instant 12- < HKCE 2{100 Paper II - 24 > Which of the following statements correctly descnbe(s) the meaning of the frequency ofa wave? 8. < BKCE 1995 Paper Il- 24 > (1) the time taken for the wave to make one complete vibration Displacement/ cm (2) the distance travelled by the wave in one second (3) the number of waves produced in one second A. (!) only 025 B. (3) only C. (!) & (2) only 1--'\--/--\--�-+Time Is D. (2) & (3) only 0. .2 0. .4 --025 13. < HKCE 2001 Paper II- 23 > Direction of +---- wavem.otion A train of water waves is generated in a ripple tank. The graph above shows the variation of the displacement of a cork R �::':',j�=k,. ,�= ==��- ===== __,,,:;:�,==-- ===== --========:=,=, placed in the water with time. Find the frequency of the waves. A. 0.2Hz B. 0.25 Hz c. 4Hz D. 5Hz Fo � corks are moving up and down on the surface of a pond as a water wave passes through them. At time t = 0, the positions of the corks are shown above. The figure below shows the displacement-time graph of one of the four corks. (Note: Displacement is positive when the cork is above the still vvater surface.) 9. < HKCE 1996 Paper II - 24 > X DWIJJacement Di,p1",emont L\ Direct;M of Vibration t ----- ----- ----- � --,. 0� V V J Time Direction of Which cork has the motion represented by the graph? propagation A. p Figurc(a) Figure (b) B. Q C. R A viOrator generates a travelling wave on a string. Figure (a) shows the shape of the string at a certain instant. Figure (b) D. S shows the variation of the displacement of a certain particle on the string with time. Which of the following expressions represents the speed ofthe travelling wave? A. X 14. < BKCE 2002 Paper II - 25 > B. y A wave source generates waves of frequency 50 Hz. How long does it take for the waves to travel 100 m? C. � A. 0.5 s y B. 2s C. 5000 s D. l'.. X D. It cannot be detennined as insufficient information is given. DSE Physics - Section C : M.C. PC-WAl-M/05 DSE Physics - Section C : M.C. PC-WAl-M/06 WAl : Wave Propagation WAl: Wave Propagation Questions 15 and 16 : A transvezse wave travels along a string with a speed of 1.2 m s-1• The diagram below shows the shape of Questions 18 and 19 : the string at a certain instant. Displacement/cm The displacement-distan.ce graphs of the particles along a travelling wave at time t= 0 and t = 0.2 s are shown below. _____.,. Direction ofwave motion Displacement at t = 0 "' 15. <HKCE 2003 Paper Il- 2S > 'Which ofthe following statements about the transverse wave are correct 'I (1) Its wavelength is 20 cm. (2) Itsfrequencyis 6Hz. (3) Its amplitude is 6 cm. A. (1) & (2) mtly Displacement at t = O 2 s B. (1) & (3) only C. (2) & (3) only D. (1). (2) & (3) \ ; I -�i-- I --1--i .+ 1--l-f l · 1-.J.�_J_,� I 16. <HKCE2003Paperll-26> 0 Distance Which ofthe following diagrnn:,.s shows the shape ofthe string at a quarter of a period later ? A. Displacement/cm B. --•' Displacem<::=cm -+- \-I· 1-:--: 1- ·I-H_J_1 .....L.LJ'-t-H-C . I -r-rLL.t ..�_J......L...L_I I LJ 2 __ 18. < HK.CE 2005 Paper Il- 34 > 10 20 30 ., l-+--+----t-c--1-+--+--+Distance/cm ,1---+----'>--+--,-+Distance/cm ., Which of the following statements about the wave are correct ? (1) Its amplitude is 6 cm. -3 ----- ----------- ----- (2) Its waveleng1h is 8 cm. (3) Its frequency is 5 Hz. D. C. Displacement/cm Displacement/cm A. (1) & (2) only B. (1) & (3) mtly 3 ----- ----------- C. (2) & (3) only D. (1), (2) & (3) 19. < HKCE 2005 Paper Il- 35 > 'What is the speed of the wave? -3 ------------------------- A. 0.2ms- 1 B. 0.3 m s-1 C. 0.4ms-1 17. <HKCE2004Paperll-22> D. 0.Sms-1 2,m The solid curve in the diagram shows a transverse wave at a certain instant After 0.05 s, the wave has travelled a distance of 2 cm and is indicated by the dashed curve. Find 20. < BKCE 2006 Paper n- 16 > the wavelength and frequency of the wave. , , In December 2004, an earthquake in the Indian Ocean caused a tsunami which produced water waves having wavelength Wavelength/ cm Frequency/ Hz about 100 m and frequency about 2 Hz. What was the approximate time taken for these water waves to trav el from the earthquake centre to Sri Lanka across a distance of about 1500 km? A. 8 2.5 A. 1 hour B. 8 5 B. 2hours c. 16 2.5 C. 3 hours D. 16 5 D. 4 hours DSE Physics - Section C : M.C. PC-WAI -M/07 DSE Physics - Section C : M.C. PC-WAl-M/08 WAl : Wave Propagation WAl : Wave Propagation 21. < HKCE 2007 Paper II -38 > 23. < HKCE 2009 Paper II - 36 > a h d e f g h j k A longitudinal wave is travelling from left to right in a medium. Figure (a) shows the equilibrium. positions ofparticles A to J in the medium. At time t = 0, the positions of the particles are shown in Figure (b). Which of the following correctly shows the displacemenMime graph of particle I? (Note: displacement to the right is taken to be positive) Figure (a) Figure (b) Figure (a) shows a series ofparticles (a - k) at their equilibrium positions. Figure (b) shows the positions of the particles at a certain instant when a longitudinal wave travels to the right passes through the particles. Which are the directions of the motion of the particles c andfat the instant shown in Figure (b) ? direction of propagation particle c particlef A. to le.ft toleft A. B. to left to right C. to right to left D. to right to right 24. < HKCE 2010 Paper II-34 > direction oftravel 22. <HKCE2008Paperll-37> ---�------,quili'briumposition a h , d f g h j k � wave trav � along a string to the left. The� abo � shows its waveform at time t = I s. 'Which of the following displa.cemenMime graphs best represents the motion of particle P ? (Take displacement upwards to be positive.) Figure (a) A. Displacement B. Displacement ah , d f g hij k Fig,,re (b) 6 ti' 2 4 ' 6 11, Figirre (a) shows a series of particles which is uniformly distributed along a slinky spring. Figure (b) shows their positions at C. D. a certain instant when a travelling wave passes through the slinky spring from left to right Which of the following diagrams: Displacement shows the correct positions of the particles after half a period from the instant shown in Figure (b) ? ab, d ' f g h ijk ti' ti' H-4 6 5 6 A. : : ri- (4 a h ,d, f g h 25. < HKCE 2010 Paper IT� 35 > Figure (a) shows the equiliorium. positions of particles E to Nin a medium. A longitudinal wave is travelling from left to B. right. At time ti, the positions of the particles are shown in Figure (b). E F G H I J K L a h ' d,f g h j Figure (a) equilibrium positions C. h ' d e fgh i j k direction oftravel D. Which of the following particles is momentarily at rest at ti ? A. K B. L C. M D. N DSE Physics - Section C : M.C. PC-WAl-M/09 DSE Physics - Section C : M.C. PC-WAl-M 110 WAl : Wave Propagation WAl : Wave Propagation Questions 26 and 27: Part B : HKAL examination questions The figure below shows the displacement-distance graph of a wave travelling to the right with speed 2 cm s- 1 at a certain instant. P and Qare two particles at distances x = 8 <:m and 18 i:m respectively. 29. < HKAL 1992 Paper I- 20 > Displacement/ cm Figure (a) ,p,___-___,,__4\J----+-PP-12\J _ l,__p_Q -.----2�------,,--• xi= Figure (b) 26. < HKCE 2011 Paper II- 34 > Figure (a) shows the etpmlbrium positions of equally spaced particles in a nwdium. A longitudinal wave travels from left to What is the period of the wave ? right through the medfum. At a certain inst.Int, the positions of the particles are shown in Figure (b). What will be the directions of.1I10tion of particle 1 and particle 7 at this instant 'l A. 0.25 s Particle 1 Particle 7 B. 4s A. to the right to the right C. 8s B. to the right to the left C. to the left to the right D. 18 s D. to the left to the left 27. <HKCE2011Paperll-35> 30. < HKAL 1993 Paper I-24 > What is the shortest tin,.e for p to have the same displacement as Q at the instant shown ? displacement A. 1' B. 3s Ol�f-=;;'s----,f,Ll _.,,--,-,;,_---➔-. time in seconds c. 4s 0.45 0.70"'-- � D. 5s A displacement-time graph of a particle in a travelling Wli'/e is shown. What is the frequency of this wave 'l A. 1.43 Hz 28. < BKCE 2011 Paper Il- 36 > B. 2.00Hz Figure (a) sbov,s a series of particles (E - 0) at their equihorium positions. Figure (b) sbo\W the positions of the particles at C. 2.22 Hz a certain instant when a longitudinal wave travelling to the right passes through the particles. D. 4.00Hz F 31. < BKAL 1994 Paper IIA-14 > Figure (a) displacement/ m dispIacement / m o o.,vo., op '0; /JL0J\_ • � t. LJo., , position/m time I ms - _. , Figure (b) !_ Figure (a) Figure(b) Which of the following statements is incorrect ? Figure (a) represents the displacement-position graph of a travelling wave at a certain instant and Figure (b) represents the A. The separation between F and N equals to the wavelength ofthe wave. displacement-time graph ofa particle in the wave. Calculate the speed of the wave. B. The amplitude of the wave is4 cm. A 300m s·1 C. J is momentarily at rest at the instant shown in Figure (b). B. 150ms·1 D. N is at the centre of compression at the instant shown in Figure (b). C. 1.2m s·1 D. 0.6m s·1 - DSE Physics - Section C : M.C. PC-WAI-M/11 DSE Physics - Section C : M.C. PC-WAI-M/12 WAl : Wave Propagation WAI : Wave Propagation 32. < HK.AL 1995Paper IIA - 12 > 35. < llKAL 2003 Paper IIA-14 > direction of propagation ofwave I I ! I I ! I 111 I I I 111 I A B ------� ----- 1 The above figure shows a longitudinal wave travelling to the right The particles and B are at the centre of a compression . The figure shows three particles P, Q and R on a transverse wave travelling towards the right The three particles will reach their own equilibrium.positions at different times in the sequence of and a rarefaction respectivel y. Which of the following gives correctly the clirectJ.ons of motion of A and B at the moment shown? A. R,P,Q B. R,Q,P Particle A ParticleB C. P,R,Q A to the right to the left B. to the right at rest D. P,Q,R C. to the right to the right D. at rest to the right 36. <HKAL2009 Paper IIA-16> 33. <BKAL 1998 Paper llA-13 > B A C Q I I l � x/cm 8 10 D The above figure shows a tnmsven;e wave propagating along a string. At the instant shown, the particle D on the string is The above :figure shows the displacement y against the position x of a transverse wave travelling to the right at time t = 0. P moving downward. Which of the follow:ingdeductions is/are correct? and Qare two particles at x = I cm and x = 9 cm �ectively, Nex.t time when Preaches its crest position is at t = 03 s. (1) The wave is propagating to the left. Which of the following statements are correct? (2) Particle B talces longer time to reach its equilibrium position than that ofparticle A. (1) The speedofthetransversewave is IO cms-1, (3) Particles C and D are moving in opposite directions at the instant shown. (2) Particle Qfust reaches its crest position at t = 0.5 s. A (!)only (3) When Qreaches its crest position,P also reaches its crest position. B. (3) only C. (1) & (2) only A (1) & (2) only D. (2 ) & (3) only B. (1) & (3) only C. (2) & (3) only D. (I), (2) & (3) 34. < HKAL 2000 Paper IlA-17 > Displacement of air particles +p Part C : BKDSE examination questions - "J� f---"�---c�/:______. ""�----,---➔) position 37. <BKDSESamplePaperlA-17> -,,,---....__p The solid curve ill the above diagram shows a triltlsverse wave 2cm at a certain instant. After 0.05 s, the wave has travelled a The above figure shows the displacement- position graph of a longitudinal wave at a certafu instant Take the displacement towards the right as positive, which of the following statements about particle Pat this instant are correct? distance of 2 cm and is indicated by the dashed curve. Find ,,--,, I', / "Y, r---- \\ the wavelength and frequency of the wave. ' (1) Pis a centre of compression. (2) P has the greatest kinetic energy. WaveJength / cm Frequency/ Hz ,/ / I I \\ \ I \, \ (3) Pis moving towards the right A. 8 2.5 ' ,,:' / A. (1) & (2) only B. (I) & (3) only c . (2) & (3) only B. C. D. 16 8 16 2.5 5 5 ',.xI/ D. 0), (2) & (3) DSE Physics - Section C : M.C. PC-WAl-M/13 DSE Physics - Section C : M.C. PC-WAl-M/14 WAl : Wave Propagation WAl: Wave Propagation 38. < BKDSE Sample Paper IA - 18 > -----�----- direction of propagation 41. < HKDSE 2013 Paper IA - 16 > displacement p - direction oftravel R The figure shows the shape of a transVerse wave travelling along a string at a certain instant. Which statements about the motion of the particles P, Q andR on the string at this instant is correct 7 The figure shows a snapshot of a section of a continuous transVerse wave travelling along the x-llirection at time t = 0. A. Particle P is moving downwards. At t = 1.5 s, the particle Pjust passes the equilibrium position for a secondtime at that moment. Find the wave speed. B. Particle Q is stati.onaty. A. 20 cms-1 C. Particle R attains its maximum acceleration. B. 12 cms- 1 D. p and Qare in phase. C. 6cms~ 1 D. 4cms-1 39. <HKDSE Practice PaperIA-17 > 2= - 42. <HKDSE2013 Paper IA-17> 2 4 5 6 7 10 11 12 13 ' , ' I-++ . : t��+:+� Figure (1) ,...,..,... • • • • • • • • • • • : rt-, 2 4 6 7 9 101112 13 ,, ,+1 .. direction of propagation Figure (2) ..,.,. A longitudinal wave travels to the right through a medium containing a series of particles. The figure above shows the +:+ � .,... :.· '..'. +!"""!"a positions of the particles at a certain instant. The dotted lines indicate the equilibrium positions of the particles. Which of the Figure (1) shows the equilibrium positions of particles a to k separated by 5 cm from each other in a medium. A longitudinal following statements about the wave at the instant shown is/are correct 7 wave is travelling from left to right with a speed of 80 cm S-1• At a certain instant, the positions of the particles are shown in (1) The wavelength of the longitudinal wave is 16 cm. Figure (2). Determine the amplitude and frequency of the wave. (2) Particles 8 and 10 are moving in the same direction. '== (3) Particle 3 is momentarily at rest amplitude frequency A. (1) only A. 2 llz •= B. (3) only B. 6 4llz C. (1) & (2) only C. 2 llz D. (2) & (3) only D. 9om 4 llz •1tlilfflflifflm 40. < BKDSE 2012 Paper IA-15 > 43. < HKDSE 2014 Paper IA-14 > abc d f ghijk direction oftravel -<------- Fi-(a) p Q ---- ------- �------ ammoom1n11• a b c def g h i j s Fi�•�) 5= A transverse wave travels towards the left on a long string. P, Q, R and S are particles on the string. Which of the following statements correctly descnbe(s) their motions at the instant shown ? A series of particles is uniformly distnbuted along a slinky spring initially. Figure (a) shows their positions at a certain (1) Pis movingupwards. instant when a travelling wave propagates along the slinky spring from left to right. Figure (b) shows their positions 0.1 s (2) Q and Sare moving in opposite directions. later. Wm.ch statement is correct? A. Particle e is always stationary. (3) R is momentarily at rest. B. Particles a and i are in phase. A. (1) only B. (3) only C. The wavelength of the -wave is 16 cm. C, (1) & (2) only D. The frequency of the wave is 10 Hz. D. (2) & (3) oruy 44. DSE Physics - Section C : M.C. WAl : Wave Propagation < HKDSE 2015 Paper IA - 12 > a b c de g h PC-WAl-M/15 I 47. DSE Physics - Section C : M.C. WAI: Wave Propagation <HKI>SE 2018 Paper IA-15 > PC-WAI -M/16 11 j The figure below shows the displacement-time graph of particles P and Q on the same transverse travelling wave of Figure (a) wavelength A. displacement ab, d g k Q p p;g,re (b) \ y " I I\ a ' h j 0 • 4 6 time/s Figure (c) \ \I I \ J\ , \ 1/\ A series of particles is uniformly distn'buted along a slinky spring initially. When a travelling wave propagates along the slinky spring from left to right, Figure (a) shows the positions of the particles at a certain instant Figures (b) and (c) Which ofthe following statements MUST BE correct? Upward displacement is taken to be positive. respectively show theirpositions 0.05 sand 0.1 slater. Which of the following is/are a possible frequency of the wave 7 (1) At it me t = 2 s, Pis mom.entarily at rest. (1) IO Hz (2) At time t = 4 s, Q is moving downwards. (2) 20 Hz (3) 40 Hz (3) The separation between the equilibrium positions ofP and Q is 0.25 ...t. A (1) only A. (2)only B. (2) only B. (3) only C. (3) only c. (!) & (2) only D. (!), (2) & (3) D. (!) & (3) anly 45. < HKDSE 2016 Paper IA -15 > a. <HKDSE 2D19 Paper IA�1 > The above figure shows a snapshot of a transverse wave which travels along a string. Which statement is correct ? A. The wave is travelling to the left ifparticle P is moving upwards at this instant. B. Particles P and Rare moving in the same direction at thisinstant. C. Particle Q is at rest at this instant D. Particle R vibrates with an amplitude larger than that ofparticle Q. 46. <BKOSE2017 Paper IA- 14> Figure (a) shows the equilibrium positions of particles E to Nin a medium. At time t = 0, a longitudinal wave starts travelling fromkftto right At time t= l s, the positions of the particles are shown in Figure (b). H J K L M N Figure(a) ·;7 ·h - =!+" : 'i-1- --i: T equiltoriumpositions M N Figure(b) , , '-\- time= 1 s direction oftravel Which of the following statements MUST BE correct? A. The distance between particles F and N is equal to the wavelength of the wave. B. The periodofthewaveis Is. C. Particle Eis always at rest D. Particle I is momentarily at rest at!"' I s. 49. <HKDSE 2020PaperIA-11> Figure (1) shows the equilibrium positions of partidcs a to kin a medium. The particles are separated by 2 cm ftom each other. A longitudinal wave of frequency S Hz is travelling fi-om left to right. At a a:.rtain instant. the positions of the particles arc' shown in Figure (2). Determine · the amplitude and spec:4 of the wave. am.pUtwle ,p«d w• A. 3.6c:m 40 cm.s B. 3.6an SOems-1 C. 2.4cm 40an s-• D. 2.4cm 80a:ns-l 50. <HKDSE 2020 Paper IA-12> The figure sbowi partoflhe m.,pt:accmcnt..distancc graph of a travelling wave of period Tat tim e t.., O, P is a pvticle on the waw. Which graph below con-ectly shows the 'VBriaf.ion of the particle's kinetic energy £ Within a period Ulmngihnnt•0'1 A. B. E T t T t :� L C. D. T t I DSE Physics - Section C : M.C. Solution PC-WAl-MS/01 DSE Physics - Section C : M.C. Solution PC-WAl-MS/02 WAl: Wave Propagation WAl : Wave Propagation HKEAA's � Schenwis p.re9an:d fot the markers' tefcrence. It should not� regmled as a set ofxnodel �wee; . Student, andteachers who are not involvedin the marking :PIQCCSS ate advised to intetpret the Marking Scheme with care. 4. A M.C. Answers T= ..!._ =_!_=0 .2s f 5 I. D II. D 21. C 31. A 41. B .-. AfterO.l s which is ±T, the wave should propagate by ½A.. C 12. B 22. C 32. A 42. A 2. 3. C 13. B 23. C 33. A 43. A 5. C 4. A 14. D 24. C 34. D 44. A ✓ (I) P and Qare two particles in phase with mmimum separation ⇒ PQ = A C 15. A 25. A 35. A 45. B ✓ (2) Pis in ma:timuJl1 displacement ⇒ PR = amplitude 5. (3) Particle P vibrates vertically about its equilibrium position, thusP will move to positionR. 6. D 16. D 26. B 36. B 46. A 7. D 17. C 27. B 37. B 47. C D 6. 8. D 18. A 28. C 38. C 48. C C 19. B 29. C 39. A 49, D 9. C 20, B 30. B 40 . B 50. C IO. R M.C. Solution (I) Pis at its maximum displacement and is momentarily at rest ✓ (2) Q is moving upwards as shown by the above diagram I. D ✓ (3) R is at the instant of maximum. displacement and is momentarily at rest 7. D R , ,,.(�\, ,,.T,\ _.,__\.,-;-. "'""·:,r"-•- '~: Q�,�---- I ' ✓ ;' : \ (1) Pis at the crest position, thus it nnist be momentarily at rest. -�-�'-P.,: ✓ (2) i Draw the dotted line representing the wave at a later instant, Q is mov ng upwards ' \ / ' ',./ \ ✓ (3) R is at the trough position, thus it must be momentarily at rest After a quarter of a period, the wave would travel towards the right a distance of a quarter ofwavekngth. 2. C 8. D In 0. 025 s, the wa.vefonnpropagatcs by¾ ofits wavelength. From the graph, T"" 02 s. - :. Period= 0. 025x4 = 0. 1 s f•.!_• 2._ dHz T 0.2 3. C ilitection of wave motion 9. C �--, ½7\:: From figure (a), A"" x. Fromfigure(b), T'"'-y. _____ .,.__,._ _____ _ �.,....-;- ---- ----�'-� -- v=f/4=!:.=3.. T y DSE Physics · Section C : M.C. Solution PC-WAl-MS/03 DSE Physics · Section C : M.C. Solution PC-WAl-MS /04 WAl : Wave Propagation WAl: Wave Propagation C 16. D f• i,211z After a quarter of a period, the waveform should propagate ¼ wavel ength towards the right. 2 Thus the crest initially at 5 cm should move to the point at 1O cm. A.= 10cm = 0.lm .·. v = p. = (2)(0.1) = o.2m s-1 17. C Wavelength: 'A, = 2 cm x 8 = 16 cm 11. D AI; the wave travels 2 cm, i.e. ½ 'A, in0.05 s which is ½ T, thus period T "" 0.05 s x 8 "" 0.40 s Frequency: f = ..!. = _l_ = 2.5 Hz T 0.40 18. A ✓ (1) Amplitude is the maximum displacement, thus A = 3 x 2 cm = 6 cm ✓ A P moves upward= the wave is travelling to the left ✓ (2) Wavelength is the minimum distance to repeat itself; thus 'A, = 4 x 2 cm = g cm ✓ B. All particles in same wave must have the same frequency ✓ C. Q is moving downwards at the instant shown (3) Since at t = 0.2 s, the wave has propagated ¾),,,,thus 0.2 s = ¾ T :. T = 0.267 s D. R is moving downwards as shown by the above diagram Frequency f = ..!. = _l_ = 3.75 Hz* 5 Hz T 0.267 12. B 19. B The time taken for the wave to make one complete vibration is the period. 3 v = E,_ = xz = 30cm.S-1 = 0.3m s-1 (1) (2) The distance travelled by the wave in one second is the speed . t 0.2 ✓ (3) The number of waves produced in one second is the frequency. 20. B 13. B By v = f/2 :. v = (2) (100) = 200ms-1 By d = vt :. (1500 X 103) = (200) t t = 1500 s"' 2hours p 21. C As shown in the above diagram, particles P, and R are momentarily at rest at t - 0 while Q is moving upwllids and S is moving downwards. Figure (a) equ:ilil>tium position Since the Displaccn:tent-tinw graph shows that the motion of cork is moving upwards at t = 0 :. Q is the answer. 14. D Figure (b) t= 0 Time taken should be found by t = d Iv. However, V = fi,, • displacement displacement ofparticle I As /. is unknmvn, v cannot be determined, so time taken to travel 100m cannot be determined. O� __ypositinn o��•- 15. A ✓ (1) The distance that the wave repeats itself in 1 cycle is 20 cm. This is the wavelength. ✓ (2) By v '°' f"J,. :. (1.2) = f (0.20) :. f = 6 Hz. Since the particle I is initially at the equilibrium position. (3) The amplitude should be 3cm from the graph.. At a later time, it would move towards the left, i.e. it would have a negative displacement DSE Physics - Section C : M.C. Solution PC-WAl-MS/05 DSE Physics - Section C : M.C. Solution PC-WAl-MS/06 WAl : Wave Propagation WAl: Wave Propagation 22. C 26. B In Figure (b), particle ais at the centre of compression, thus it must be at the equihOrium position. Wavelength: IL, = 8 cm After half a period, particle a shouldperform half a cycle, By v - f' .·. (2) = /(8) :. f= 0.25Hz thus it must be still at the same equih'brium position but it then becomes at the centre of rarefaction. Period: T= .!. = _l_ - 4, J 0.2s The graph in option C show s that particle a is at the rarefaction and at the same position, thus it is the answer. 27. B 23. C Particle b andj are at the centre of compression and par ticlefts at the centre ofrarefaction. The wave is moving towards the right, thus particle P is moving downwards. They are at the equilibrium positions. To reach the position of Q, that is the crest, particle P has to move through ¼ cycle. Thus, the fune taken is f T. After a small time interval, the wave travels towards the right and is r epresented by the dotted line. :.t=¾x4=3s Particle b and together with particle c nearby are moving towards the right Particlefis movin g towards the left. 28. C Particle Jis at the position of rarefaction, thus it must be at the equilibrium position. 24. C At equilibrium point, it must move with the maximum. speed, not at rest. Thus option C is incorrect. tlirection oftravel _'w ____ �--- �P___ � . . on --------- eqw"liibriumpos., 29. C Tak e the rightward direction as(+) : l e. The wave would travel towards the left after t = 1 s as shown by the dotted in It shows that particleP is at the equilibrium position and is moving downwards at t = 1 s. Particle I is moving towards the negative direction, thus it is moving to the left. Thus, option C shows the correcty - t graph for particle P. Note that position of Patt = I s. Particle 7 is moving towards the positive direction, thus it is moving to the right 25. A 30. B Period: T = 0.70- 0.20 = 0.5 s E '., ; " time = ti I=.!.= __1__ = 2Hz T 0.5 direction oftravel 31. A From the graph, E and Mare at the centre of rarefaction and I is at the centre of compression. From Figure (a), particles separated by0.6 mare in the same phase, thus the wavelength : IL,= 0.6 m Centr e ofrarefaction and centre of compression must be at the equil ibrium pos itions and are moving at greatest speed. From Figure (b), a partic le takes 2 ms to complete a cycle For a particle to be momentarily at rest, it must be at the extreme point, T=2xI0-3s 1 and its position should be at the middle of the compression and rarefaction. J =}.. = - - = sooHz T 2xI0- 3 l ftmost position and must be momentarily at rest at !1. From the graph shown, particle Kis at the e V ""f/L, = (0.6) (500) = 300 m S-1 DSE Physics - Section C : M.C. Solution PC-WAl-MS/07 DSE Physics - Section C : M.C. Solution PC-WAl-MS /08 WAl: Wave Propagation WAl : Wave Propagation 32. A 37. B Take the rightward direction as(+) : Wavelength: /1. = 2 cm x 8 = 16 cm As the wave travels 2 cm, i.e. ½ /1. in 0.05 s which is ½ T, Period T = 0.05 s x 8 = 0.40 s Frequency : f = l = _l_ = 2.5 Hz T 0.40 Particle A is moving towards the positive direction, thus it is moving to the right. OR Particle Bis moving towards the negative direction, thus it is moving to the left. As the wave travels 2 cm in 0.05 s, speed: v = !!.. = � = 40 cm. s-1 t 0.05 33. A By V = JA :. (40) = I (16) :. f= 2.5Hz 38. C • A. M P is at the crest, it must be momentarily at rest. B. M Q is at the equilibrium position, it must have the maximwn speed and must be moving. ✓ (1) Particle D moves downward ⇒ the wave moves to the left ✓ C. MR is at the extreme position, its acceleration is the.maximum. (2) A moves upward before going downward but Bmoves downwatd only ⇒ A : takes a longer path to reach the equih'britunposition D. M the separation between P and Q are not n A, they cannot be in phase. (3) C and D both move downward. 39. A 2 5 11 -10.,.-- 12 13 34. D 3 4 6 7 ��L ,, ........ : """""' ✓ Pis a centre of compression rightwards (1) ,__ . since the particles at the left hand side of P have positive displacement, i.e. moves to the right ; ���: _ .... ---: ��� ..� : .. 1 � .. while the particles at the right hand side ofP moves to the left. • • • • • • ✓ P:atequihl>riumposition ⇒ maximumKE 4 5 6 7 10 11 12 13 (2) ✓ Draw the displacement- position graph as shown in the above figure. (3) p: has(+) displacement later ⇒ moving to the right Note that particles 3 and 11 are at the compression and particle 7 is at the rarefaction. ✓ (1) The separation between two compressions is 1 wavelength. :. A = 8 x 2= 16 cm 35. A Af. the installt shown, particle P is momentarily atrest, particle Q and R are moviog downwards. • (2)' After a short time, the wavewould move rightwards to the dotted position. Thus, particle 8 is moving leftwards and particle 10 is moving rightwards. Time for P to reach the equilibrium point = ¼T They are moving in opposite directions. Time for Q to reach the equih"briu!n point > ¼ T • (3) Particle 3 is at the equilibrium position, it must have the maximum speed, but not at rest Time for R to reach the equihnrium point < ¼ T 40. B 36. B • A. For a travelling wave, particles maybe momentarily at resl There is no particle that is always atresl ✓ At this instant, P is moving downwards. ✓ B. In Figure (a), particles a and/ are both at the compression, thus they are in phase. As it takes 0.3 s for P to reach the crest position that performs ¾ cycle, the period is 0.4 s. • c. The separation between a and i is one wavelength, which is 32 cm.. Wavelcngth ofthewaveis4cm. Speed= ;\,IT= {4)/(0.4)=10cm s-1 • D. Particle a is at the compression in Figure (a) and at the rarefaction in Figure (b), (2) At t"" 0.5 s, Q should reach its trough position. that is, particle a has moved through half cycle of the oscillation, thus the time taken is half period. ✓ (3) The separation of P and Q is two wavelengths, thus their motions are in phase. tr=0.ls .·. T=0.ls :.f=liT=1!0.2=5Hz DSE Physics - Section C : M.C. Solution PC-WAl-MS/09 DSE Physics - Section C : M.C. Solution PC-WAl-MS/10 WAl : Wave Propagation WAl : Wave Propagation 41. B 45. B From the graph, wavelength: /2 = 30 - 6 = 24 cm • A Ifparticle Pis moving upwards, the wave should be travelling to the right In 1.5s, particle P performs ¾ cycle, thus it talces a time of¾ T, where Tis the period. ✓ B. Ifthe wave is moving to the right, then bothP andR are moving u.pwards. :. T = 2s Ifthe wave is moving to the left, then both P and R are moving downwards. Thus, they must be m oving in the same direction at this instant Frequency: f = ..!.. T = .!. 2 = 0.5 Hz • C. Particle Q is at the equilibrium position 1hat bas the greatest speed, it must be moving. Speed : v = fJ. = (0.5) (24) - 12 cm s- 1 • D. Particle Rand Q should be moving with the same amplitude since it ls a travelling wave. 42. A 46. A From Figure (2), particles b andj are at the centres of compression. ✓ A. From Figure (b), bothE and Mare at the centre of rarefaction, Separation between them is the wavelength. thus distance between E and Mis one wavelength. :. /4 = 8x5 = 40cm Therefore, distance between the next particles, F and N, is also one wavelength. Byv = fli ;. (80) - /(40) ;. f- 2Hz • B. There is no information concerning the period or frequency of the wave. From Figure (2), as particle bis at the compression andparticle/is at the rarefaction, they are at eqnilibriwn positions. • c. In a travelling wave, there is no particle that is always at r est. Particle d should then be at the extreme position. • D. Particle I is at the centre of compression, it is moving towards the right at this instant. Displacement ofparticle dis the arnplitude. .-. Amplitude = 6 c m 47. C ✓ (!) At t = 2 s, P is at the position of trough, thus it must be moinentarily at rest 43. A ✓ (2) A t t = 4 s, Q is at equilibrium positon and later at a lower position, thus it must be moving downwards. After a while, the wave would shift to the left shown as the dotted Cl,lt'l'e. • (3) P and Q are neither in phase nor anti�phase,, there is no phase relation oonceming tbcir separation. ✓ (!) Particle P is moving upwards. (2 ) Particles Q and S should move in the same direction. (3) Particle R is not momentarily at rest, but mo ving downwards. 44. A In Figure (a), particle e is at the centre of compression. ✓ (!) fff= lOHz,then T= I.=..!__= 0.1s. Afteratirneof0.05s: t = �T= fT, / 10 U particle e should travel ½ cycle to the position of the centre of rarefaction as shown in Figure (b). Thus,f= 10HzispossiOJe. (2) Iff= 20Hz,then T= _!_= 2.. = 0.05s. Afteratimeof0.05s: t =IT, / 20 p article e should travel I cycle to the position of the centre of compression, but not the rarefaction as shown in Figure (b). Thus,/= 20 Hz is imp ossible. (3) If f= 40Hz, then T= _!_ = 2.. = 0.025s. Afteratimeof0.05 s: t = 2 T, / 40 particle e should travel 2 cycles to the position of the centre of compression, but not the rarefac tion as shown in Figure ( b). Thus,/= 40 Hz is impossible. DSE Physics - Section C : Question PC-WAl-Q/01 DSE Physics - Section C : Question PC-WA1-Q /02 WAl : Wave Propagation WAl : Wave Propagation Part A : HKCE examination questions 2. <HKCE1990PaperI�5> A vertical vibrator generates waves on a string. It takes 0.25 s to produce a complete wave of wavelength 1. < RKCE 1981 Paper I - 6 > 0.8 m on the string. (a) Find the frequency and speed oftbe waves on the string. (b) How longdoes it take for the wave to propagate a distance of2 m ? (2roarks) (c) The figure below shows the shape of the string at the instant vrl1en the vtDrator has made one complete vibration. A transverse wave is travelling steadily from left to right through a series of particles. At a certain��� vnve fonn is as shown in the above figure. Each ofth.e vt'bratingparticles is observed to perform four complete oscillatLons m 16 s. � Directionofwavemotion Direction of t (a) Find the following quantities: Vibration ,J, (i) the amplitude ofthe wave, D I- 0.Sm ----J.j (u) the wavelength. (i) At the instant shown, whlch ofthe particles A, B,. C, Dis/are (1) moving downwards, (iii) the period, (2) at rest? (2marks) (iv) the frequency. (ii) Sketch the shape of the string after 0.125 s. In your figure sh.ow the positions of the particles A, B, C andD. (4nurrks) (b) At the instant shown, which of the particles P, Q, R, S, T is/are (5 marks) (i) moving upwards, (il) moving downwards, (iii) momentarily at rest? (c) What will be the position of particle Q a qtlazter of a period later 'I DSE Physics - Section C : Question PC-WAl-Q/03 DSE Physics - Section C : Question PC-WAl-Q/04 1 WAl : Wave Propagation WAl : Wave Propagation 3. <HKCE1998Paperl-7> 3. (c) (iii) Find the amplitude and wavelength of the wave. (2-k,) Figure I '. ;; {iv) If each particle takes 0.25 s to complete one oscillation, find the speed of the wave. ,, ..i..11..tt:L1.1...1..Li..:J..J�i.·d:H:r2 _ ,_l-i£B A Iongitidi.nal wave is travelling from left to right in a medium. Figure 1 shows the equilibriuDl positions of some particles A _ _ to Kin the medium. Figure 2 shows the positions of the particles at a certain time t when the wave 1s passmg through them. (a) What is meant by a longitudinal wave? Give an example of a longitudinal wave. (2 marks) (b) Point out a particle in Figure 2 which is 4. < HKCE 2002 Paper I - 4 > (l) at the centre ofa comp ression, (ii) at the centre ofa rarefaction. (2m&ks) Q ----------· Equilibriuznposition p {c) The table below shows the displacements of particles A and B at time t. (Note : Displacement to the right is taken to be positive.) 0.3m ---- (i) Using Figures 1 and 2, :find the displacements of the other particles and complete the Table below. (2 maxks) A wave is generated on a string. The figure above shows the shape of the string at a certain instant At this instant, both particles P and Qare moving downwards. (a) State the type ofwave generated on the above string. (I :mark) (nj In the figare below, draw agraph showing the displacements of the particlesalongthewave at tune t. · (2 marks) J¼tf·' Displacement/cm ' (b) What is the direction of1l:aveI of the above wave? (l=k) \-J� -i , ·cr-i-,r rc, f ' (c) At the instan.t shown, which particle (P or Q) has a greater speed? Explain briefly. (2mawJ (d) Find the wavelength of the wave. (1 DWk) _, (e) Describe the motions ofparticlesP and Q at a quarter of a period later. (2 maw) -10 DSE Physics - Section C : Question Solution PC-WAl-QS/01 DSE Physics - Section C : Question Solution PC-WAl-QS/02 WAl : Wave Propagation WAl : Wave Propagation HICEAA's Matking Scheme is� for the ntarkets' xefert:nce. It should not be regarded as a set of model answers. Students and tcacheis who ate not mVolved in the marlting process are advised to inte;rJltet the Matking Scheme with care. 3. (c) (i) [2] Particle C D E F G H I J K Question Solution Displacement/ cm -8 -6 0 6 8 6 0 -6 -8 I. (a) (i) A= 2cm [l] (ii) 'A.= 8cm [l] (ii) (iii) T=4s [l] (iv) f = 025 Hz [l] (b) (i) R,S [2] (u) P,T [2] (ili) Q [l] (,) Q is at 2 cmbelow its present position [2] -5 2. (a) Frequency = 4 Hz [l] Speed=!!._""� = 3.2ms-1 t 025 OR v=f/2=4x0.8=3.2ms-1 [2] _10 'iti:1=1==:TF;./:0, t:r+.-·-i��ti#.Jfflt:+=l::¥ +1 · +· . (b) By d = vt [l] < Correct points > [l] _-. (2) a (3.2) I t = 0.625 s [l] < Correct curve > [l] (,) (i) (1) A (iii) Amplitude= 8 cm [!] Wavelength = 80 cm (2) BandD [l] (iv) speed = /A, [1] (u) D < For wave fon:n > [2] 1 a --x0.8 "'3.2mS-l [l] _______!: -------- ----------- < 0.5 mark for each particle> [2] 0.25 4. (a) It is a transverse wave [1] 3. (a) A longitudinal wave is a wave in which the 'Vibrations are parallel to the direction of trave l of the wave. [1] (b) The direction is towards the left. [l] Example: (Any ONE of the following) [l] (,) ParticleP has a greater speed, * [l] Sound waves since it is at theequiblmum position. [l] * Ultrasonic waves * Waves generated in a slinky spring (d) Wavelength= o3 = 0.2 m [l] 1.5 ( b) (i) ParticleA (OR J) i satacentreofcompression. [l] (e) Particle P is momentarily at rest. [l] (u) Particle Eis at a centre of rarefaction. [l] Particle Q is moving downwards. [l] Hong Kong Diploma of Secondary Education Examination DSE Physics - Section C : MC. PC-WA2-M/01 Physics - Compulsory part ( ;t,/,-<fl5,'- ) WA2 : Wave Phenomena Section A-Heat and Gases (��#t.ittt:) 1. Temperature,Heatandinternalenergy(il:..if., #..'fl'liit) 2. Transfer Processes (�ff.$i1Ht) Part A : HKCE examination questions 3. ChangeofState(�/!!./1-Jtt�) 4. General Gas Law (-t�.ifi.:ttit.#) 1. < HKCE 1982 Paper Il-12 > 5. Ki.netic Theory (¾Til�Ur) A train ofwater waves is travelling froma deep water region to a shallow water region. Which ofthe following properties of Section B -Force and Motion (h�.il!�) the water waves will be changed ? L PositionandMovement(1Jt.'l;fo-$t!i) (l) wavelength 2. Newton'sLaws(4'ij(;t.#") (2) frequoncy 3. Moment ofForce (:hif.) (3) velocity 4. Work,EnergyandPower(,ft.;I;, �:i'fl'-Wll!l-) A (I) only 5. Momentum ($';-:I) B. (3) only 6. Projectile Motion (�tti!J&i) C. (1) & (3) only 7. Circular Motion (l!l!J!Jilf») D. (2) & (3) only 8. Gravitation (31 iJ) Section C- Wave Motion (1;t$!,) I. Wave Propagation (iltliH/liiJ!.) ,. <HKCE 1982 Paper II� 13 > 2. WavePhenomena(it�JP..�) A stationary wave is obtained by attaching one end ofa string toa 50 Hz 3. Reflection and Refraction ofLight(;\;.11\l.&.MJl#Af) vibrator as shown in the diagram. The velocity ofthe waves propagated 4. Lenses (.i!::lt) in the string is 5. Wave Nature ofLigbt (;\;.11-Jilttii#·!i.) A. 0.1 m s- 1 6. Sound(¾%) B. 0.2ms- 1 �I 0.Im Section D - Electricity and Magnetism ( ii!��) C. Sm s-1 L Electrostatics (Mi-'IJ!:�) D. 10 ms-1 2. Electric Circuits ( 't4) 3. Do mestic Electricity (;f<:.ls Jfl 1£) 4. MagneticField(.ittljj-) ,. < HK.CE 1983 Paper II- 23 > 5. Electromagnetic Induction ( 1l!:��.ii,) A stationary wave is set up alonga string by a vibrator as shown 6. Alternating Current (5U1.i. 'ii!:) in the diagram. If the frequency of the vibrator is 5 Hz, what is vibrator the velocity of the wave setup in the string? Section E -Radioactivity and Nuclear Energy (�:f#j{.�:fi,;tt:�) A. 25 cm s-1 1. Radiation and Radioactivity (�Af:f,,�Af.W.. �) B. S0cms-1 I<--- 20cm � 2. Atomic Model (�-r.m?I:!) C. 75 cms- 1 3. Nuclear Energy (-ltt/lg,) D. IO0cms-1 Physics - Elective part (�1f� f;-) Elective 1 -Astronomy and Space Science (it.:t.$:faNi.*#4':) 4. <.HKCE 1984 Paper Il- 22 > L The universe seen in different scales (�!SJ :irr-,1M'f.T"9o/WimYr.) In a ripple tank experiment, a series of plane water waves are sent through a narrow slit Which of the following will have 2. Astronomy through.history (XX,$/r,11t&:t) changed when the water waves emerge from the slits? 3. Orbital motions under gravity('Jt.jJf{jg$Jr.;t.;(i?)) (I) wave speed 4. Stars and the universe (,rJ.£:f,,o/'ili) (2) wave pattern Elective 2 -Atomic World (Jfi,f-ilt!/f..) (3) :freq uency I. Rutherford's atomic model (,i�#Z.lf.-r�1'!) A. (1) only 2 Photoelectric effect( 16 ·utit) B. {2) only 3. Bohr"satomicmodel ofhydrogen (.it.Ii "9.&,J.f.7-il�) C. (I) & (2) only 4. Particles or waves ($.-:;-*it) D. (2) & (3) only 5. Probing into nano scale («.ffi.#J;fH!l;·.¾'l,.) Elective 3- Energy and Use ofEnergy (Ji6itf<>115iJf.�fi:.}ij) I. Electricityathome(Ulfi'll!:) 5. < HK.CE 1985 Paper II - 25 > 2. Energy efficiency in building (�1/i,/r,l�l,IJltt.$) A stationary wave is produced ina string bya vertical vibrator as shown P A 3. Energy efficiency in transportation (�fti#lil.r��tt.Jil.) in the diagram. If P is at the crest of an antinode at a certain instant, (V\J 4. Non-renewable energy sources (�"f.jl}!t�i,lli) what is the direction ofmotion of the point A at that in5tant? 5. Rmewable energy sources ("f .jl},:l�62fJ A. upwards viDrator Elective 4 - Medical Physics ( U.�#JJ;t/ffe) B. downwards wall I. M.ucing sense ofthe eye (O!l{ig/& '!{) C. to the right 2. Makingsenseoftheear(.lf-lr,i�'a') D. momentarily at rest 3. Medical imaging using non-ionizing radiation ( .'/� 'lt4/t#.M i}*:%1l$) 4. Medical imaging using ionizing a r diation (11l:�ffiMY<¥:ifll*) ·., DSE Physics - Section C : MC. PC-WA2-M/02 DSE Physics - Section C : MC. PC-WA2-M/03 1 WA2: Wave Phenomena WA2: Wave Phenomena <BKCE 1986Paper ll- 24 > 11. < BKCE 1990 Paper ll-26 > 'Which of the following properties of Straight waves in a ripPle tank are observed using a hand stroboscope with a single slit The maxinnun frequency of rotation In a ripple tank experiment, a series of plane 'Water waves passes through a narrow slit. of the stroboscope where a stationary pattern can be observed is 2 revolutions per second. The distance between the first the waves will remain unchanged? crest and the eleventh crest is found to be 0.2 xn. What is the speed of the wave 7 (1) speed A. 0.2 m s-1 B. 0.2 m s-1 (2) direction of travel 11 10 (3) frequency A. (1) only D. 0.4 ms-1 B. (2) only 10 c. (1) & (3) only D. (2) & (3) ool y 7. < RKCE 1987Paper Il-12 > p p The figure shows a stationary water wave at its maximum vibration. 12. <BKCE1990Paperll-23> What is the direction of the motion of a particle P at this instant 7 A. towards the right == =Aas�=r.,,',,==Q B B. upwards C. downwards = D. momentarily at rest above. Which of the following A straight pulse AB is travelling towards a straight barrier PQ in a ripple tank as shown a=, = Q figures best shows the :reflected pulse? 8. <HKCE 1988Paperll-24> B. 7 A. P======Q P===aa�=;ec 30 In a ripple tank, when water waves pass through a narrow gap in a barrier, what happens to its frequency and wavelength? Frequency Wavelength A. increases decreases B. decreases increases C D. = p C. decreases remains unchanged D. remains unchanged remains unchanged =====,7 =,=,, Q 9. < HK.CE 1989 Paper 11-25> 13. <HKCE1991Paperll-24> The figure above shows the wave pattern in a ripple tank from coherent point sources S1 and S2. What kind of interference occurs atX, YandZ? A series ofwater waves, generated in water of uniform depth, is travelling towards an obstacle as shown above. Which ofthe X y z following diagrams best shows the wave pattern after passing the obstacle? a c n �1111 A A. destructive constructive constructive �jj jj �j j j J �j J j j B. no interference constructive constructive C. no inootference destructive no interference D. no interference destructive constructive 10. <HKCE1989Paperll-26> 14. < HKCE 1992 Paper 11-24> In a ripple tank experiment, the pattern of plane water wave� is frozen by �ing a � stroboscopic lamp flashing at a freqllency of 50 Hz as shown m the above diagram. DJ If the frequency of the vibrator is 50 Hz, find the wavelength and speed of the waves. A stationaiy wave is formed in a string. The above diagram shows the string at the instant of maximum displacement. What will be the shape ofthe wave pattern one quarter of a period later ? Wavelength Speed A R C A 4om 2ms-1 B. 4om 12.5 ms-1 C. Som 2.5 JllS-1 D. Som lOm s-1 PC-WA2-M/04 PC-WA2-M/05 1 DSE Physics - Section C : M.C. DSE Physics - Section C : M.C. WA2 : Wave Phenomena WA2 : Wave Phenomena IS. < HK.CE 1992 Paper ll 25 > 18. < RKCE 1993 Paper n .23 > pm R R S• J�3on � so M best Plane water waves travel towitrds a straight barrier PQ as shown in the figure above. Which of the following diagrams In a doubie-1;li t experiment, a source S sends waves towards two slits P and Q, which are equidistan.t:fromS. The distances of shows the re.fleeted waves ? a point M:fromP and Qare 53 cm and 50 cm respectively. If constructive interference occurs at M; the possible wavelength A. B. of the waves is A. I cm. B. 2cm. c. 4cm. �Q �Q D. 6cm. tttH C. D. 16, < HKCE 1992 Paper ll 26 >R Obstacle Shallow Deop region region < HKCE 1994 Paper n- 20 > 6f A vibrator generates a stationary wave on a string. The tA The figure above shows a series of plane water waves travelling in a shallow region of water. The waves pass through a small diagram shows the string at an instant of maximum r-------g� ---·7r slit to a deep r egion of water. Which of the following diagrams shows the wave pattern in the deep region? displacement. Which of the following statement is coi:rect? Drr,ctio A. R C � jl))) A. Particle Pis moving towards the right ofVt1trati�., B. Particle Q is moving u pwards. c:, Particle R always remains at rest. Vt"hrator Fixed end n:' All particles in the string move with the same amplitude. r 20. <HKCE 1996Paperll-25> Vibrator 17. <HKCE1993PaperIIR25> \ I� I \--\ ..._ �-----_--17 Figul'e(a) Figun(b) (0J_____l____i'.0\ A vibrator generates continuous plane waves in a ripple tank (see Figure (a)). Fi gure (b) shows the wave pattern. observed. p N Q Two vibrators P an.d. Qare set to vibrate in phase in a ripple tank. MN is the perpendicular bisector ofPQ as shown above; 'Which of the following statements is/are true? (1) Constructive interference occurs along MN (2) Destructive interference occurs alongPQ. (3) A crest is always formed at M A (1) only B. (2) <m!y C. (I) & (3) only D. (2) & (3) only DSE Physics - Section C : M.C. PC-WA2-M/061 DSE Physics • Section C : M.C. PC-WA2-M/07 WA2 : Wave Phenomena WA2 : Wave Phenomena -I 21. < HKCE 1997 Paper TI - 25 > ZS. <HKCE1998Paperil-26> pass the obstacle, they bend A series of plane water waves travel towards an obstacle in a ripple tank. When the waves around the corners of the obstacle. \Vbich of the following statements is/are correct? (1) The phenomenon is called diffraction. {2) The speed of the waves remains unchanged as they bend round the comers. (3) The degree of bending of the waves depends on the size of the obstacle relative to the wavelength of the waves. A. (1) only B. (1) & (3) only A vt'brator generates continuous plane waves in a ripple tank. The waves undergo diffraction when they pass through a slit. C. (2) & (3) only Which of the following can increase the degree of diffraction of the waves? D. (!), (2) & (3) (1) Increasing the width the slit :L (2) Placing the vibrator closer to the silt (3) Increasing the wavelength ofthe water waves 26. <HKCE 1998 Paper Il- 25> A. (1) only B. (3) only C. (1) & (2) only Shallow '' D"I' regi. on D. (2) & (3) only region \ of water. Which of Questions 22 and 23 : A vibrator generates a stationary wave on a string. The diagram below shows the string at a certain instant. The diagram above shows a series ofplane water waves travelling from a shallow region to a deep' region the following diagrams best shows the wave pattern in the deep region ? A. B. Direction ofvi'bration t ---------- X----------y ----------- Vibrator Fixed end 22. <HKCE 1997 Paper D- 23 > Which of the following statements is incorrect? A. The distance betweenX and Yis equal to half the wavelength of the stationary wave. B. All particles betweenX and Yon the string vi'brate in the same direction. c. D. C. All particles between X and Yon the string vibrate withthe same frequency. D. All particles betweenX and Yon the stting vioraf:e with the same amplitude. 23. <JIKCE1997Paperll-24> The vt"bratilig string also sets the neighbouring air into vibration. Which of the following statements about the waves on the string and those in air must be correct ? A. They are both stationary. B. Theyhavethe same speed. C. They have the same wavelength. D. Theyhavethesamefrequency. 27. <HKCE1999Paperll-22> 24. < BKCE 1998 Paper Il - 27> lm ------,-; Direction l ofvibra.tion Vibrator Fixedend :: to obtain the waves as A series of straight water waves travels towards the right in a ripple. tank as shown above. In order A vibrator generates a stationary wave on a string. The above diagram shows the string at the instant of maxim.um shown in the right hand side, what kinds of phenomenon have the straight waves undergone ? displacement \Vbich of the following statements is incorrect ? A. reflection only A. Particles P and Q move with the same amplitude. B. The motions of particles P and Qare in phase. B. refraction only C. Particle Q is momentarily at rest at this instant C. diffraction only D. The wavelength of the stationary wave is 0.4 m. D. refraction and diffraction only DSE Physics - Section C : M.C. PC-WA2-M/08 DSE Pbysics - Section C : M.C. PC-WA2-M/09 WA2 : Wave Phenomena WA2 : Wave Phenomena 28. <HKCE 1999 Paper Il- 23> 32. < HKCE2001 Paper Il- 25 > A plane water wave travels from a de ep region to a shallow region of water. If the wavelength, frequency and speed of the wave in the deep region are A1, Ji and vi respectively, while the corresponding values in the shallow region are ,t2 , fi. and ,�:.:., Vz respectively. Which of the following relations is/are correct? (1) A1 > A2 (2)v1> V::! (3) Ji > fi A. (!) only In the above diagram, XYrepresents a boundary between a deep region and a shallow region of water ma ripple tank. A B. ( 3) only series of straight water waves in the deep region travels towards XY. Wbicli of the following diagrams best shows the wave C. ( 1) & (2) only pattern in the shallow region ? D. (2) & (3) only A. B. 29. < HKCE 2000 Paper D - 26 > A water wave of frequency 30 Hz travels in a deep region of water. '\Vhen the wave enters a shallow region, its wavelength is reduced to one-third of its original value. Find the frequency ofthe waterwave in the shallow region, A 30Hz B. 60Hz C. 90Hz D. It cannot be determined since the speed of the water wave is not given. C. D. 30. < BI{CE 2000 Paper II - 27 > p t Q A straight pulse PQ travels: towards a V-shaped barrier in a ripple tank as shown above. Which of the following diagrams best shows the reflected pulse(s) ? 33. <HKCE2002Paperll-24> A. B. In a ripple tank experiment, a series of water waver travels towards a barrier. Which of the following quantities would �-// remain unchanged after the waves are reflected by the barrier ? "°' (1 ) wavelength � (2) frequency � (3) speed ( A. ! ) & (2) on ly B. (1) & (3) only C. D. C. (2) & (3) only D. (!), (2) & (3) 34. < 8KCE2002 Paper II- 26> Rippletimk S},Qngy lining 31. < HKCE 2001 Paper Il - 26 > Water waves of wavelength A, are diffracted as they pass through a gap of width d as shown in the figure above. Which of the following changes would produce the most significant diffraction Plane water waves - A. ' remains unchanged d halved OpeJJing Which ofthefollowingphenomena would be observed when the water waves pass through the opening in the above set-up? A. reflection B. remains unchanged doubled B. refraction C. halved halved C. diffraction D. halved doubled D. interference DSE Physics - Section C : M.C. PC-WA2-M/10 DSE Physics - Section C : M.C. PC-WA2-M/11 WA2 : Wave Phenomena WA2 : Wave Phenomena 35. < HK.CE2003 Paper II- 27 > 37. <HKCE2004Paperil-23> / obstacle --. Plane water waves travels towards an L-shaped barrier in a ripple tank as shown above. Which of the following diagrams best shows the reflected wave pattern ? l]] ripple tank A a '--------"-----� A student uses the above set-up to study the diffraction of water waves. Vlhich of the following changes can make the diffraction effect more significant? (1) reducing the width of the gap between the obstacles (2) increasing the frequency of the viOrator (3) adding more water to the ripple tank A (1) only B. (2) only C. (1) & (3) only D. (2) & (3) on ly c. D. 38. <HKCE 2004 Paper 11-25 > Two dippers S1 and Sl are cowiected to the same vtlxator and produce identical waves in a ripple tank. Pis a point such that S1P - SiP= ,t, where ,l is the wavelength of the water waves generated. Which of the following statements is/are correct ? (1) Constructive interference occurs at P. 36. < HKCE 2003 Paper 11- 28 > (2) A crest is always formed at P. Obstacle (3) If the wavelength of the waves generated by the dippers is doubled, destructive interferen ce will occur at P. A. (1) only B. (2) only C. (1) & (3) only D. (2) & (3) only 39. < HKCE2004 Paper Il- 21 > Doop Sh,llow region region --- --• equilibrium position Q p Plane water waves travel from a deep region to a shallow region of water through a narrow gap as shown above. Which of the following properties of the waves remains unchanged? The figure shows the waveform ofa transverse stationary wave at a certain instant. Ifparticle Pis at its lowest position at this instant, what will be the instantaneous motion of particles P and Q after a quarter of a period 'l """ A direction of travel p Q B. A. moving upwards at rest C. wavele ngth B. moving upwards moving upwards D. frequency C. at rest at rest D. at rest moving upwards DSE Physics - Secti.on C : M.C. PC-WA2-M/12 DSE Physics - Section C : M.C. PC-WA2-M/13 I WA2 : Wave Phenomena WA2: Wave Phenomena 40. < HKCE2005 Paper II. 36 > 43. <1IKCE2006Paperll-15> An interference pattern is formed by two coherent point sources of water waves. Which of the following variations can change the positions of constructive interference ? (1) changing the amplitude of the waves medium.A (2) changing the wavelength of the waves (3) changing the separation between the point sources A. (!) & (2) only mediumB B. (1) & (3) only C. (2) & (3) only D. (!), (2) & (3) A series of plane waves travel from medium A into medium B. The figure above shows the positions, PQ and P'Q', of� 41. < BKCE 2005 Paper II - 14 > wavefront before and after entering the medium.B. What woold happen to the speed and the wavelength of the wave when it 'travels from medium A to medium.B? Speed Wavelength / A. increases increases B. increases remains unchanged C. decreases decreases D. decreases remains unchanged Straight water waves travel towards a barrier as shown above. Which of the following diagrams best shows the reflected 44. < BKCE2007 Paper n -16 > wave pattern? light source l A B. Light trwels from air to water through a slit as shown above. Which of the properties of the light in water remain(s) unchanged? (I) direction oftravel (2) speed (3) frequency C. D. A (1) only B. (3) only C. (!) & (2) only D. (2) & (l) only 45. <BKCE 2009 Paper 11-14> � direction of wave propagation 42. < BKCE 2005 Paper II - 15 > - - - =---- - - ---- -: oo,k --;�- --,:�-�-:-: --�:- ---- -,:��------- ---- A cork floats in water and a dropper is used to produce circular waves as shown in the diagram. Vlhich of the following describes the motion \ckopp« of the cork when the waves pass through it? - A. moves towards the dropper 0 0 A cork is floating on a calm water surface as shown in the above figure. At time t = 0, a "'.3-ter wave is travelling towards the co� with a speed of0.2 m s·1• When will the corlc rise to its highest position for the first time? --- ---'-----------'1------------- B. moves away from the dropper C. Vibrates vertically about its original position A 3.00 s B. 3.50 s D. moves away from the dropper and vibrates vertically at the same .____ ___ ______ _____________________________ ____ ______ ___.._._-___ time C. 3.75 s D. 4.00 s DSE Physics - Section C : M.C. PC-WA2-M/14 DSE Physics - Section C : M.C. PC-WA2-M/15 WA2: Wave Phenomena WA2 : Wave Phenomena 46. < BKCE 2009 Paper ll - 38 > s, s, Solid �es represent�· S1 and S2 are two narrow gaps The figure above shows the wavefronts formed in a rip�le tank. statements tS correct? The figure above shows the circu1at wavefronts produced by two identical dot vibrators, S1 and S2, in a ripple tank at time allowing water waves to pass through and interfere. Which of the followmg t = O. Solid lines represent crests. A cork is placed at point P on the water surface. Which of the following graphs best A. Refraction occurs when.water waves pass through S1 and S2. represents the variation of the displaceme:at s ofthe cork with time t'l (Take upward as the positive direction.) at the moment sbown above. B. The displacementofthe water particles atP and Qare the same A. s R C. Constructive imerference occurs at Q. D. The water particle atP is always at a crest. ot-----------+ Part B : HKAL examination questions 50. <HKAL 1990 Paper I- 16 > IV d,op p shallow c. D. Ot-----------+ towards the inte rface PQ betw� a shallow re�o� and a The fi�e shows wave crests moving in the direction of the arrow one ofthe wave crests m the deep region . h m· •"- fim=. deep region ass own o.w, o--· Which of the lines shown may represent 47. <HKCE 2009 Paper II- 37> A. I A musical note is produced by a guitar string. 'Which of the following properties about the sound wave produced and the B. Il wave in the string is/are the same? ,C. ill (1) wavelength D. IV (2) frequen cy (3) wave speed A. (!)only 51. B. (2) only C. (1) & (3) only D. (2) & (3) only 48. <HKCE2010Paperll-36> Two point sources S1 and S2 are producing cireularwaterwaves in a ripple tank. The :6gw-e shows the wave pattern at a certain instant. Solid lines repre sent crests and dotted lines represent the frequencyf ofthe vi'brator. Wbich of the troughs. Which ofthe following statements is/are correct? In the above figure, a stationary wave is set up on an elastic string by adjusting (1) The water particle at A is always at rest. following statements is/are correct? . . . of antmodes m the wave pattern mcreases. (2) The water particle at B is always at a crest (1) If/increases so that another sta.tioruuywave is.set�• the number (3) The interference at C is neither constructive nor (2) If/increases, the speed ofthe waves on the stnng mcmises . . v.raves on the stnng. destructive. (3) The waves produced in air by the strillg have the same speed as the A. (1) only A. (!) only B. (2) only B. (3) only C. (1) & (3) only c. (!) & (2) only D. (2) & (3) only D. (2) & (3) only PC-WA2-M/16 PC-WA2-M/17 DSE Physics - Section C : M.C. 1 DSE Physics - Section C : M.C. 1 WA2: Wave Phenomena WA2 : Wave Phenomena 52. <BKAL 1996PaperllA-12> 56. <HKAI.2011) Paper llA-14 > The waves from two coherent sources must have (1) the same amplitude (2) the samewavelengfu (3) a constant phase relationship A. (!) only B . (3) only s, C. (!) & (2) only D. (2) & (3) only s, 53. <HKAL2001PaperllA-12> In which of the following cases can the principle of superposition be applied to two overlapping waves of the same nature ? (I) Two waves that have the san,.e amplitude. (2) Two wave s that travel in opposite directions. Figure (a) Figert (h) (3) Two waves that are coherent. the same frequency. Figure (a) �ows the pa� of water A. (I) & (2) only In a ripple tank, s1 and S2 are nvo coherent sources VI'brating with . waves. Figure (b) shows the displacement-time gtaph of B . (I) & (3) only waves at time t"" O. The solid lines represent the crests of the water correct for the particle R at mid-way between. PQ as •,�, •,�, c,)A:., •,�, C. (2) & (3) only the particle P. Vilbich of the tollowing <lisplacement-fune graphs is D. (!), (2) & (3) shown? 54. <HKAL2005 PaperllA -29 > p x ___J= -- y 57. < HKAL 2012 Paper lIA-15 > ofthe same nature : The principle ofsupruposition can be applied to two overlapPingwaves (l) only if they have the same frequency. Two identical transverse waves, travelling in opposite directions along stringXY fued at both ends, fonn a stationary wave . (2) only lf they have the same amplitude.. i The separations between.Xand Y s 45 cm. Particle Pis an anti.node with an amplitude of 2 cm. The above figure shows the (3) onlylftheytravel in the Slime direction. shape ofthe string at an instant when P is at its maximum displacen:ient from the equilibrium position. What is the amplitude A. (I) & (2) only and the wavelength ofeach of the travelling waves on the string ? B. (I) & (3) onlY C. (2) & (3) only Amplitude Wavelength n: None of the above conditions is necessary. A 1cm 30cm B. 1cm 15cm C. 2cm 30cm D. 2cm 15cm Part C : BKDSE examination questions 55. < BKAL 2009 Paper llA -15 > 58. · < Hl(DSE Sample Paper IA-19 > The diagram shows the wavefronts of a wave passing the boundaty of two different media. Which of the following combinations about the String XY is fixed at both ends. The distance between X and Y is type of wave and the two media is/are possible? 45 cm. Two identical sinusoidal waves travel along..l'Y in opposite directions and form a stationary wave with an antinode at p oint ... typeofwave mediUIIll medium2 medium! P. The figure shows the.string when Pis 2 mm, its maximum '""" ... displacement, from the equilibrium position. What is the '21Dlplitude (!) light waves medium2 and wavdeogth of each of the travelling waves on the string ? (2) sound vro.ves ware, Amplitnde Wavelength (3) waterwaves shallow water deep water A. (I) only A. Imm 30cm B. (3) only B. Imm !Som c. (!) & (2) only c. 2mm 30 "" D. & (3) only D. 2mm !Som (2) 1 DSE Physics - Section C : MC. PC-WA2-M/1'11 DSE Physics - Section C : M.C. WA2 : Wave Phenomena WA2 : Wave Phenomena 59. < BKI>SEPractice Paper IA -19 > )r.- <HKDSE2014PaperIA-16> a gap in a sea A stationary wave issetup along a string by a vibrator. The waveform The photograph shows a series of plane seawaves travelling through waves remains at a certain instant s i shown. lfthe frequency of the vibrator is 50 Hz. wall which exhi.Oits diffraction. Assuroing that the frequency of the vibrator "! what si the wave speed along the strin g ? unchanged, which of the following will i ncrease the degree of diffraction A. 15ms- 1 (1) Thegap in the sea wall becomes narrower. B. 30ms""1 (2) The wavelength of the waves increases. C. 4Sms-1 �) The amplitude ofthe waves becomes larger. ·n. SSm s-1 A. (!) & (2) only wall B. (1) & (3) only C. (2) & (3) only 60. < HKDSE 2012 Paper IA-18 > ··D. (!), (2) & (3) 01 63. < HKDSE 2014 Paper IA- 13 > · Imm t� · _:rtI Uzf1 rl r- A stationary wave is funned on stri ng fixed a t both endsX and Y. The above figure is a snapshot of the string at time t= O. The amplitude of vibration at an an.tin.ode is A. If upward displacement is taken as positive, which of the following shows the displacement-time graph ofpointPon the string for one period ? displacement water falling in a ripple tank. The pulses are thenreflected 1I The above figure shows two circular pulses produced by drops of c by a straight barrier. Whi h diagram bes t shows the r eflected pulses? ,B. A IfH]fflf- C. D. I D. c. 61. <BKDSE2013PaperIA-18> p Q t 64. <JJKD� 2015PaperlA-13 > R Two waves p and Q travel in thesame direction and meet at a point displacement Toe graph shows the variation of the displacetnent of each wave with . time at that poi nt. Which ofthe following statements 15/arecorrect? -, A vibrator generates a stationazy wave on astring which is :fixed at one end. The figure shows the appearance of thestring at (1) P and Q have the same frequency. ,\ I acertain instant Which of the following descriptions aboutthe motion of particles P, Q andR must becorrect? 7 (2) The oscillatio n due to Pis in anti-phase with that due to Q. (1) P and Qare momentarily at rest at this instant.. (2) Q and R take the same timetoreach their respective equilibrium positions. (3) The amplitude of the resultant wave at that point i s four 0 � " times the amplitude of P. (3) P andR are always in ant:iphase. ' A. (1) only · A. (1) only B. (3) only B. (3) only c. (!) & (2) only C. (1) & (2) only D. (2) & (3) only D. (2)&(3) only DSE Physics - Section C : M.C. PC-WA2-M/201 DSE Physics - Section C : M.C. PC-WA2-M/211 WA2 : Wave Phenomena WA2 : Wave Phenomena 65. <HKDSE 2015 Paper IA-18 > 68. <HKDSE2017PaperlA-16> The figure shows plane water WKVCS travelling from region X to region Y. The wavelengths of the water waves in regions X and Yare4 cmandS cm respectively. Region% Region Y A String is set to vibrate at .frequency /such that a standing wave is formed between two fixed supports X and Y as shown in the above figure. If the tension in the string is increased by adding wtight _gradually while the frequency is kept atf, which ofthe following is a possible mode of vibration at a steady state ? A. B. y Which of the followin.gstatemerrts is correct? A. The speed of the water waves in region Xis higher than that in region Y. C. B. Toe direction of travel of the water waves bends to"('ll'ds the normal as they ent ef region Y. C. The frequency of the water waves is the same in botltregions. D. If plane water waves of wavclengtb 5 cm travel from region Y to region x; the wavelength becomes 6 CJJl after the D. waves enter region X: 1 , t 69. <HKDSE 2017 Paper IA-17> In which of the following simauons MUST the direction of travel ofa wave change ? 66. <HKDSE 2016 Paper IA-16 > (1) when a wave is reflected by a barrier = - - - - -.-:=�:f=�==-- -.-:::::ff=:�-:--- The su:rfer in the figore reaches a crest at the moment shawn. {2) 'Ml.en a wave enters from one medium to another medium The crests of the water wave are 20 m apart and the surfer dirootion oftravel (3) when a wave travels through a gap smaller than its wavelength descends a vertical distance of 4 m from a crest to a trough in a time interval of2 s. What is the speed of the wave ? - --- A. (1) & (2) only A. lms-1 B. 2ms-1 = B. c. (1) & (3) only (2) & (3) o,tly C. 5mS-1 D. (1), (2) & (3) D. lOm s-1 70. <HKDSE2018PaperIA-16> 67. < HKDSE 2016 Paper IA - 18 > Light undergoes diffi:action round an obstacle. A string is tied to a vibrator while the other en dis :fixed to a wall A stationary wave is fon:ned as shown. light------'>- uwidth X The angle of diffi::a,ction would increase ml.en y (1) the amplitude of the incident light is increased. (2) the width. ofthe obstacle is increased. Which statement is c0trect when the frequency of the vz'btator doubles? (3) the wavelength of the incident light is increased. A. The wavelength. will double. B. The wave speed will double. A. (2) only C. The amplitude will be halved. B. (3) only , • D. Particles X and Ywill beeome vtOlating in phase. C. (1) & (2) only ,;,. (1) & ( 3) only DSE Physics - Section C : M.C. PC-W2-M/22 A DSE Physics - Section C : M.C. Solution PC- WA2-MS / 01 WA2 : Wave Phenomena WA2 : Wave Phenomena , HKBAA'sMarltlng Scheme is PICParedfor 1he IWIIkcts' rcfcccnce. It should not be xe gamed as a set of model answers. 71. < HKDSE 2018 Paper lA - 18 > m ! Students and teachem who aie not involved the IlUlrki:ng process are advised to inte:rp,ret the M.ai:king Scheme with care. The figure shows a string with one end fixed and the other ead tied to a vforator A stationary wwe . is funned as shown at a certain. fre quency. M.C. Answers '� 1. C 11. C 21. B 31. A 41. D 2. D 12. D 22. D 32. A 42. C �m�Rsb Ifthe speed ofthe wave along the string is 7 m s-1 , whatis the frequency of the wave ? 3. B 13. B 23. D 33. D 43. A A. 2.8Hz 4. B 14. C 24. A 34. C 44. B B. 7Hz C. 17.5 Hz 5. D 15. A 25. D 35. D 45. C D. 35Hz 6. D 16. A 26. A 36. D 46. D 7. D 17. A 27. D 37. C 47. B 72 . <HKDSE 2019 Paper IA-15> 8. D 18. B 28. C 38. C 48. A 9. B 19. C 29. A 39. A 49. C 10. B 20. B 30. D 40. C 50. C 51. A 61. D 71. C 52. D 62. A 72, A 53. D 63. B 7 . 54. A 64 . A 7 . A 55. C 65. D 56. C 66. C 57. D 67. D 58. A 68. C 7 • <HKDSE 2019 Pa per IA-16> 59. B 69. B 60. D 70. B M.C. Solution 1. C ✓ (1) From deep to shallowwaterregion., the wavelength would decrease. )< (2) The frequency would remain unchanged durin g refraction. ✓ (3) The veloci ty would decrease when water wave travels from deep to shallow w-ater region. : 2. D A= 0 1 . :x2 = 0.2m A. 3 B. 4 V = f,t "' (50) (0.2) = 10 Ill s-l C. 6 0. 7 7 • <HKDSE 2019 Paper IA-18> DSE Physics - Section C : MC. Solution l'C-WA2-MS /02 DSE Physics - Section C : M.C. Solution PC- WA2-MS /03 WA2 : Wave Phenomena WA2: Wave Phenomena 3. B C Distance between 2 adjacent nodes is equal to half of a wavelength. ✓ For the same medium, the same speed is unchanged. (1) .'. (4) X .': = (20) :. A.= 10cm Diffraction occurs when the wave passes through the slit and spreads out to give a change of direction. 2 (2) :. v =f,1. = (5) (10) = SOcms-1 ✓ (3) Frequency is unchanged during diffraction. 4. B 12. D -7 (1) San:ie medrom gives the same speed. ✓ (2) 'When the wave passes through nauow slit, diffi'action occurs, giving a change in wave pattern. (3) Frequency is unchanged during diffraction. B Draw the dotted line that the incident pulse appears to be. 5. D Then reflect the dotted line to give the reflected pulse. The reflected pulse should be at the right side oftbe barrier. P is at the crest, thus P is momentarily at rest. For a stationary wave, all particles within the same loop are in phase, thus A is also momentarily at rest. 13. B All the figures in A, B, C give proper diffi::act.ion pattern. 6. D However, since it is unifonn depth, there is no change in speed, thus no change in wavelength Distance between the 11 crests = 10/1. .-. B is correct since the wavelellgth. remains the same. :. /1.= �:m - 14. C v = f A= (2 )x(0.2) = OA ms 1 10 10 Wavelcngth : A==20==5Clll 4 7. D Speed: V = jJ."" (50)(0.05) = 2.SmS-1 As the stationazy wave is at its maximum vi'bration, each particle is at their extreme positions with maximum displacement, thus each particle is momentarily at rest. 15. A 6.=53-50=3cm 8. D For constructive interference to occur, 6. = n 'J,. where n = 0, 1, 2, .... Frequency: no change in source ⇒ no change in frequency A If'),.= 1 cm, then A = 3 cm = 3 'J,,,, thus constructive interference occurs. Wavelength : no change inmedium ⇒ no change in speed ⇒ no change in wavelength B. If'),.= 2 cm, then A = 3 cm = 1.5 'J,,,, thus destructive interference should Oct:Ur. C. If'),.= 4 cm, then 6. = 3 cm = 0.75 'J,,,, thus neither constructive nor destructive interference occurs. 9. B D. If'),.= 6cm, then I:,. = 3 cm = 0.5 '),,,, thus destructiveinl:erl"erence should occur. x, A= 1I,i - U = �,i :. No interference 4 4 16. A y, /:J. = 1_!.il. -1]_1 = Oil Constructive interference A, B, C give proper diffraction pattern. 2 2 Afu:r the wave passes through the slit, it is a deep region, thus the wave speed increases, and the wavelength increases. z, A=2A-Ll=Lt Constructive interference 17. A 10. B ✓ Path difference at any point on MN "" 0, tlms cons!Jllctive intetference occurs along MN. (1) For stationary wave, after ¾ period, the particles at antinodes will be at the equih"brium positions. Alternate constructive and destructive interference occurs alongPQ (2) Therefore, the waveform will become a horizontal line. (3) Crest and trough can both be formed at points of constructive interference. DSE Physics - Section C : M.C. Solution PC-WA2-MS/04 DSE Physics - Section C : M. C. Solution PC-WA2-MS/05 WA2 : Wave Phenomena WA2 : Wave Phenomena 18. B 25 D . ✓ (1) Bonding araund the comers is diffraction ✓ <,) No change in depth of water, thus no change in medium, giving no change in speed ✓ The increase of wavelength gives greater degr ee of diffraction (3) 26. A No changein medium, thus no change in speed and no change in wavelength. !9. C A. ParticleP v.ihtates vertically about ts equilibrium position only; at this iostant, P is momentarily at rest i Qis anode, thru, t is alway s at rest B. i ✓ c. Risa node, thus it is always at rest Shallow -> deep ⇒ speed inmases D. P has the maximum amplitude while Q has zero amplitude . ⇒ wavelen gth increases ⇒ imgle made with the boundazy increases 20. B Tilting =::> at middle is the same depth but increasing depth to the right and decreasing depth to the left 27. D ⇒ increasing wave speedto the right and decreasing wave speed to the left Wavelength.decreases⇒ speed decreases⇒ refraction.occurs :::::> increasing wavelength to the right and decreasing wavelen gth to the left The wave bends round corner :::> diffraction occurs 21. B ' 28. C (1) Increase ofwidth gives smaller degree of diffraction. Waterwavetravelsfasterindeepregion ⇒ vi >vz (2) is correct ' <,) Degree of diffraction is independent ofthe position of the source. No change in source ⇒ J; ::. fz (3) is not correct ✓ In.crease of the wavelength gives greater degree of diffraction (3) = (l) is con-ect By v f/1. :::> A 1 >A2 22. D 29 . A ✓ A. The distance betweenX mui Y, i.e . distance between 2 nodes, is half of the wavelen gth The change of medium results in refraction, but in refraction, th.eie is no change in frequen cy ✓ B. Alltheparticles within the same loop vibrate in pruse, thus vibrate in the same du"eci:i.on. Frequency remains the same of30 Hz ✓ C. All particles in the same wave vibrate with the same frequency . ' D. Differentparticles have different amplitudes in a stationary wave . 30. D 23. D The wave on the string and the wave in airhave the same frequency as they come from the same source. t 24. A 31. A A. At this mslant, Pis the antinode which has the maximum amplitude . Q has smaller amplitude . The most signi.ficant diffraction effect occurs when ✓ B. Particles in the same oop must move in the same phase l © wavelength.is greater ✓ C. g is at maximum &placement and must be momentarily at rest @ slit size is smaller ✓ D. Since distan.ce between2 nodes is half ofthe wavelength which is 0. 2 m : A= 0. 4m :. A is the best choice. DSE Physics - Section C : MC. Solution PC-WA2-MS/06 DSE Physics - Section C : M.C. Solution PC-WA2-MS I 07 WA2 : Wave Phenomena WA2 : Wave Phenomena 32. A 40. C Water wave in shallow region travels with a smaller speed, thus the v,,,avelength i s decrea;ed. (1) Changing the amplitude ofthe waves would not affect the positions of conttructive interference Vii'hen entering the shallow region, it moves a shorter distance, thus bending occurs. ✓ (2) II. t ⇒ separation between two lin� of constructive interference t ✓ (3) Separation between the point sources -l, ⇒ separation between two lines of constructive interference t 33. D ✓ (1) By v ""j')... asvandfremainunchanged, A. is unchanged. 41. D ✓ (2) Frequency depends on source only, so it is unchanged. ✓ (3) Speed depends on medium only, so it is unchanged. 34. C Diffraction occurs when water waves passes through a small opening. 35. D During reflection, incident angle = reflected angle Note that both the incident angle and the reflected angle equal 60 °. 42. C Since water wave is a transverse wave, Consider the direction of travel oftbe wave, the wave reflects two times and travels backwards. the co:rk would oscillate vertically up and down about its original position. 36. D 43. A • A During diffraction through the nan-ow slit, As shown in the above diagram. 0a > eA the direction of travel changes from one direction to many direction by spreading out from the slit. • B. The speed decreases when the water waves travel from deep region to shallow region. During refraction : sin e oc v oc ,t. mediumA • C. The vvavelengtb decreases when the water waves travel from deep region to shallow region. : . vs > VA and An > AA x· P' \Jg, ✓ D. The frequency remain.s unchanged during diffraction and refraction. mediumB �\Y' Q' 37. C ✓ (1) A smaller gap can give greater degree of diffraction. 44. B • (2) By increasing the frequency, the wavelength is decreased. Thus, the degree of diffraction is decreased. (1) Direction of travel would change after diffraction from the slit. ✓ (3) By adding more water, depth is increased,. thus speed is increased, wavelength is then increased. (2) Speed would change after refraction as the light travels from air to water. Therefore, the degree of diffraction is increased. ✓ (3) Frequency depends on the source only, it remains unchanged during refraction and diffraction. 38. C 45. C ✓ (1) Since the path difference atP is equal to 1 t,,, constructive interference occurs at P. • (2) At points of constructive interference, ctem: or trough 'f1lB'J form. ✓ (3) Ifthe wavelength is doubled, path difference: b = ½ (ZA,), thus d.ettructive interference occurs. 39. A P is an antinode. After a quarter of a period, it is at the equi.h"briUlll. position. At that instant, it shm.tldmove upwards. Distancedbetweenthenearestcrestand thecork = 0.15+0.6 = 0.75m Q is a node. It is always at rest. By d = Vt ... (0.75) - (0.2) t :. t = 3.75s DSE Physics - Section C : M.C. Solution PC-WA2-MS/08 DSE Physics - Section C : M.C. Solution PC-WA2-MS /09 WA2: Wave Phenomena WA2: Wave Phenomena 46. D I D I 53. I At the time instant shown, pointP is at the trou gh position of wave I and also trough position of wave 2. Principle of Superposition can be applied to : Thus it is at the lowest position. all i,pes ofwaves wrth different :frequency, amplitude, directions and phas Moreover, trough and trou gh give s constructive interference, thusP is at constructive interference. 54. A I 47. B 0) Amplitudeofeachtra:ve llin.gwave "' ½ A= 1 cm As the wave speed depends on the medium, sound wave in air and the wave in the string should have different speeds. (l) Wavelengthofeachtravellingwave "' 45x j = 30cm As the two wave s come from the same source , they must have the same frequency. By v = fJ, they must have different wavelength. 55. C As the wavelength inmcditn:n l is longer, the wave in medium 1 has great er speed. 48. A ✓ light waves travel with greater speed in IU1' than in water ✓ (1) At A, crest meets trough to give destructive interfere.nee, thus th e p:micle there is always at rest. • ✓ sound waves traVel with greater speed in water than in IU1' • (2) AtB, crest meets crest to give constructive interference, B then vibrates with the greatest amplitude . However , B would be sometimes at the crest and sometin1es at the trough as it vibrates up and down. water waves travel with smaller speed in shallow water than in deep water • (3) From the graph, S1 C = 125 A and S2 C = 2.25 A. Path &:ffetence at C = 225 A - 1.25 A = l A. Thus C is at constructive interference. 56. C p has crest on crest andR has trou gh on trough, both ofthem have coostruotive interference. 49. C At t "' O, dis placement ofR is negative since it is at the trough positiw. • A When water wavespass through Si and S2, diffraction occurs . • B. P is at the crest, with positive displacemen t; Q is at the U'OUgh, with negative displacement 57 D ✓ C. Q is at the position of trough on trough, thus give greater trough to have constructive interference. • (1) Two waves with different frequency can be supeiposed. The path difference at Q = 3.5 A-2. 5 A = 1 A :. constrnctiveintetferenceoccurs atQ • Two waves with different amplitude can be supecpos ed. • (2) D. At this instant, Pis at the cres t, but later the displacement ofPwould vary, it1t1ay be at the trough later. • (3) Two waves in opposite directions can be superposed. The princ iple of superposition can be applied to any two waves of the same natw:e. 50. C N ,hallow - p Water wave in dee per region moves with a greater speed. SB. A :.vd>v,:::;-8,i>t?, :. m is the possible wavefront N is not correct since the wavefront makes a refracted angle greater than 90° with the boundary, which is impossible . Q (l) Amplitude 51. A The stationary wave is formed by two travelling waves in opposite direction supexpose together. ✓ (1) ft⇒ A-i- ⇒ numberofloopslncreases ⇒ numberofantinodesonthestringt • (2) Speed on the same medium is constant, not affected by the change of frequency . The amplitude of each travelling wave should be 1 mm so that they add tog ether to give the antinode of2 mm. • (3) The two waves are in different medium, they have different speed. @ Wavelength = 45 x ½ = 30 cm 52. D • (1) Waves from two coherent sources ma y have simil;l.r amplitude , due to different path lengths . 59. B ✓ (2) Two coherent sources must have same frequency, thus same wavelength. Wavelen gth: A = 90 x ½ = 60 cm = 0.6 m ✓ (3) Two coherent sources must have constant phase relationship. Speed : v "' Ji,. = (50) (0.6) = 30 m s-1 DSE Physics - Section C : M.C. Solution PC-WA2-MS/ 10 DSE Physics - Section C : M.C. Solution PC-WA2-MS ill WA2 : Wave Phenomena WA2 : Wave Phenomena 60. D 66. C P is at the extreme point, that is, the crest of its oscillation at t = 0. /2 = 20m From crest to trough, it is ½ cycle, thus it takes a time of ½ penod. 61. D .-.tT=2s T = 4s (!) P and Q may not reach the exb:emc positions, thus they may not be momentarily at rest ✓ (2) Q and R are in antiphase (opposite phase), they reach their own equilibriwn positions at the same time. Speed of the wave: ✓ (3) P andR are at adjacent loop, they must always be in antipbase. v=�=�=Sms-1 T 4 62. A OR ✓ (!) Ifthe gap is narrower, the degree of diffraction will increase. f• 2_ • '- • 0.25Hz T 4 ✓ (2) As the wavelength of the waves increases, the degree of diffraction will increase. v =f/2= (025)(20) = Sm s-1 (3) The degree of diffra¢tion is not affected by the amplitude of the waves. 67. D 63. B A. "\Vb.en the frequency doubles, the wavelength should become halved. The wave grows llll.til it is reflected by the walls. B. The wave speed is not affected by the frequency, thus it should be unchanged. Use dotted line to show the incident pulse behind the walls. C. The amplitude is not affected by the frequency, thus it should be uncb3!1ged. The reflection of the dotted pulse gives the reflected pulse. ✓ D. "\Vb.en frequency doubles, the wavelength becomes halved. The number ofloops in the stationary wave changes from.4 loops to 8 loops. Particle Xis 5th loop and particle Y is in the 7th loop, counted from the vi'brator. '' Particles in these two loops are all vibrating in phase. ' 68. C ' '' • A. During refraction, speed vis proportional to wavelength /4. As the wavelength in Xis smaller, the speed of water wave inX should be smaller than that in Y. • B As shown in the figure, the direction of travel in region Y should be bent away from the normal. ✓ C. The frequency of wave IIlUSt remain unchanged during refraction. 64. A ✓ As shown in the figure, the period T of the two waves are both 4 divisions, • D The ratio ofwavelengths in the two regions should remain unchmged. Thus, the ratio should be 4: 5, but not 5 : 6. by / "" ,!_, they have the same frequencyf. T (2) WhenP is at the cre$t, Q is not at the trough, thus they are no in anti-phase. 69. B ✓ (!) When a wave is reflected, it direction must change. (3) The amplitude ofP is 1 division and the .amplitude of Q is 3 divisions. Since the two waves are not in phase, • (2) When a wave enters from one medium to anothermedi\llll, refraction occurs. the amplitude of their resultant wave would not be the sum of their individual amplitudes, During refraction, the direction may not change if the angle of incidence is 0° along the normal. thus the amplitude of their resultant wave would not be 4 divisions, that is, not 4times of that ofP. Thus, the direction may not change during re:frac:tion. ✓ (3) When a wave travels through a gap, diffraction occurs. 65. D The wave spreads out through the gap, thus the direction must change. As the tension in the stting is increased, speed of the transverse wave along the string increases. ; 70. B Since the frequency is unchanged, • (!) Degree of diffraction is not affected by the amplitude ofthe wave. by v = fA, the wavelength incteases. • (2) To increase the degree of diffraction, width of obstacle should be decreased. The only option that shows an increase of wavelength of standing wave is D. ✓ Longer wavelength gives greater degree of diffr:acti.on. I (3) PC-WA2-MS/12 PC-WAl-Q/01 1 DSE Physics - Section C : M.C. Solution DSE Physics - Section C : Question WA2: Wave Phenomena WA2 : Wave Phenomena 71. C Part A : HKCE examination questions There arc S locps in the statiollal)'wave. The length of each loop is 0.5 A. :. Sx0.54 = I I. < IIKCE 1979 Paper I� 6 > :. A= OA m (a) What are the uses ofthe following parts of a ripple tank in wave expcriments ? Byv=fA (i) a dot vibrator, (1 =<k) (7) • J (0. 4) :. f= 17.SHz (ii) the shallow portion of the tank. (iii) the spongy lining around the edges of the tmk (1 mark) (b) In a ripple tank experiment, waves are generated by a straiglrt vtDrator as shown below. refiecting bamer ,i '� '❖ shallow portion :i •,< ,, ,;,. sponge limllg edge might vibrator (i) In the above figure, sketch the wave pattern at the shallow portion of the tank. (ii) What phenomena occur in the shallow portion of the tank ? PC-WAJ-Q/02 PC-WA2-Q/03 1 DSE Physics - Section C : Question DSE Physics - Section C : Question WA2: Wave Phenomena WA2 : Wave Phenomena 2. < HK.CE 1984 Paper I- 5 > 3. <BKCE1985Paperl-5> In a ripple taDk. experiment, a generator produces a train of straight waves travelling towards a bani.er with tvlo narrow slits. In a ripple tank experiment, a train of water waves are produced by a straight vibrator of frequency 10 Hz. The train of waves The distance between two successive wave crests is found to be 2 cm. goes from region A to another region B through a straight boundary PQ as shown in the figure below. The two regions are of different depths. The distance betWeen two successive crests of the waves in region A is O.o3 m while that of the waves in the (a) The ripple tank is illuminated by a stroboscope lamp. The wave motion appears to be stationary when the frequency of region Bis 0.02 m. the stroboscope lamp is 10 Hz What is the speed of the train of waves ? (3 marks) p (b ) region A regionB (a) Describe briefly how to set up two regions of different depths in a ripple tank. Two sources St and Sz vibrating in phase give out water waves. The above figure shows the pattern of water waves at a (b) Describe briefly bow to measure the distance between the crests of two successive v.ravefronts. (4marks) certain instant. (i) Explain why the energy of the water waves is at a maximum at points A and E and is at a minimum at points B and.D. (4marks) (c) Find the speeds of the trains of water waves in (i) regionA, and (ll) Since very little or no wave motion is seen at points B and D, a student concludes that energy disappears there. (U) regionB. (4nwks) Explain briefly where the energy goes. (2 marks) (d) Which of the regions, A orB, is deeper 7 (fu) Sketch the water level along the line XC at the above .instant. (2marks) (e) If a barrier Xis now placed in position RS as shown in the figure, which wave pbenome11on would occur 7 Sketch the wave pattern that you expect to observe. (2 marks) (iv) How would the separation between A and C change if (1) the frequency of the generator increases, and (2) the separation betmen the two sources increases ? (2 """") DSE Physics - Section C : Question PC-WA2-Q/04 DSE Physics - Section C : Question PC-WA2-Q/05 WA2 : Wave Phenomena WA2 : Wave Phenomena 4. < BKCE 1989 Paper I - 5 > - 5. < HKCE 1990 Paper I - 5 > A vertical vibrator generates waves on a string. It takes 0.25 s to produce a complete wave ofwavdength 0.8 m on the string. 1ttrcc{;=-,';";,J{ (a) Fmd the frequency and speed of the waves on the string. (3 m>ttks) (b) The figure below shows the shape of the string at the :instant when the vibra.tcr has rnade one complete vibration. A B Im B --,, Dkectmnofwavemotion Direction A t -------- A glass tank is filled with a liquid. A cork is placed at the mid-point of the tank as shown above. A vibrator Xis moving up C and down at the surface producing straight waves. Vib:tion (a) Describe the motion of the cork. (! marl<) vibrator D 1- 0.8tn � (b) Suggest a Slmple method of measuring the wavelength of the wave using a stroboscope. (i) At the instant show.rt, which of the part:iclesA,B, _C, Dis/are (3 marl<,) (1) moving downwards, (2) atrest? (c) It takes 2 s for the waves generated by Xto reach the opposite end AD of the tank. During this tillle interval, the vibrator makes 5 'up' and 'down'. Find (ii) Sketch the shape of the string aftet 0.125 s. In your figure show the positions. ofi:he perticlesA, B, CandD. (,) the frequency, �----------------------- (4ma,-ks) -, ( ii) the wavelength, and (iii) the speed of the wave. (6marks) (c) A certain pointP on the string is fixed to the wall so that a stationary wave is foIIIled The figUre below shows the string at the instant of maximtun displacement (d) If another vt"bratcrplaced at the opposite end AD is also moving in exactly the same way as X, what will be the change in the amplitude of the movements of the cork? Explain briefly. (3 marks) ,�::.�.Jr"� vfbrator (i) Describe the motion ofparticlesXand Yat this instant (,) If the tank is tilted so that A is higher thanB and Xis moving as before, sketch a dwgram to show the wave form that would be observed when viewed from the sideABCD. (n) Sketch the shape of the string after one quarter on a cycle. (4marl<s) (2 marl<,) (d) The vi1,rating string in (c) also sets the neighbouring 1lir VJ.orating. List two differences between the wa;ves in air and those on the string. (.2 marks)