5. WAVE MOTION & SOUND

1) The human ear is most sensitive to sound in the frequency range of

A) 20 to 20000 Hz B) 200 to 400 Hz C) 1000 to 2000 Hz D) 10000 to 20000 Hz

2) An echo repeats two syllables. If the velocity of sound is 330 m/s, then the distance of reflecting

surface is A) 16.5 m B) 33.0 m C) 66 m D) 99 m

3) A boat at anchor is rocked by waves whose crests are 100 cm apart and whose velocity is 25

cm/sec. These waves reach the boat once every A) 0.25 sec. B) 4 sec. C) 25 sec. D) 15 sec.

4) A certain broadcasting station broadcasts at frequency of 12 Mega Hz. The wavelength of waves

emitted is A) 25 m B) 2.5 m C) 36 m D) 3.6 m

5) A sound wave has frequency 500 Hz and velocity 350m/s. What is the distance between the two

particles having phase difference of 600 A) 0.7 cm B) 11.6 cm C) 70 cm D) 120 cm

6) Velocity of sound in air is 300 m/s. Then the distance between two successive nodes of a

stationary wave of frequency 1000 Hz is. A) 10 cm B) 20cm C) 15 cm D) 30cm

7) There are three sources of sound of equal intensities with frequencies 400, 401 and 402 Hz. The

number of beats per seconds is A) 0 B) 1 C) 2

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D) 3

8) The velocity of sound in gas in which two waves of wavelength 1.0 m and 0.01 m produces 4 beats/sec. is A) 360 m/s B) 404 m/s C) 1010 m/s D) 440 m/s

9) A fork of unknown frequency when sounded with another fork of frequency 256 Hz produces 4

beats/sec. The first fork is loaded with wax. It again produces 4 beats/sec. When sounded together with the fork of 256 Hz frequency, then the frequency of first tunning fork is A) 260Hz B) 252 Hz C) 252 or 260 Hz D) None of these

10) Two tuning forks of frequencies 250 Hz produce beats. If a maximum is produced just now, after

how much time the minimum is produced at the same place

A) 181

s

B) 241

s

C) 61

s

D) 121

sec.

11) 56 tuning forks are arranged in a series that each fork gives 4 beats/sec with the previous one. The

frequency of last fork is 3 times that of first. Then frequency of first fork is A) 52 Hz B) 56 Hz C) 60 Hz D) 110 Hz

12) A tuning fork produces 4 beats/sec. with 50 cm and 40 cm of a stretched wire of a sonometer. The

frequency of fork is A) 36 Hz B) 50 Hz C) 90 Hz D) 110 Hz

13) Two waves represented by Y1 = a1 sin wt and Y2 = a2 cos wt are superimposed at a point at a

particular instant. The amplitude of resultant wave is A) a1 – a2 B) a1 + a2

C) 221

2 aa

D) 22

12 aa

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14) The fundamental frequency of an open pipe is N keeping the pipe vertical. It is submerged in

water so that half of its length is filled with water. The fundamental frequency of air column is A) N B) N/2 C) 2 N D) 3 N/4

15) If a star emitting orange light moves away from the earth, its colour will

A) appear red B) appear yellow C) remain the same D) turns gradually blue

16) A tuning fork of frequency 500 Hz is sounded on a resonance tube. The first & second resonances

are obtained at 17 cm and 52 cm. The velocity of sound in m/s is A) 170 B) 350 C) 520 D) 850

17) A whisting engine is approaching a stationary observer with velocity 110m/s. The velocity of

sound is 330 m/s. The ratio of frequencies as heard by observer at the time of approaching and passing of engine is A) 4 : 3 B) 3 : 6 C) 4 : 1 D) 2 : 1

18) When a wave undergoes reflection at rarer medium then it undergoes a phase difference of

A) (a) B) (b) /2 C) (c) 2 D) (d) No change in phase

19) The frequency of the third harmonic of a closed organ pipe is equal to which of the overtones?

A) first B) second C) third D) none of above

20) A stretched string fixed at both ends has n nodes then the length of string in terms of wavelength is

A) n 2

B) (n + 1 ) 2

C) (n – 1) 2

D) n + 21

2

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21) Two waves of wavelength 1m & 1.01 m produce 10 beats in 3 sec. The velocity of sound in a gas

is about A) 33 m/s. B) 300 m/s. C) 337 m/sec. D) 1120 m/sec.

22) The spectral line for a given element in light received from a distant star is shifted towards longer

wavelength by 0.32 %. What is velocity of star if c = 3 108 m/s A) 9.6 104 m/s. B) 9.6 102 m/s. C) 9.6 103 m/s. D) 9.6 105 m/s.

23) Wavelength of the wave is the distance between two particles of the medium having a phase

difference of A) /2 B) 2 C) 3 /4 D) Zero

24) Longitudinal waves cannot be propagated through

A) a gas B) a liquid C) vacuum D) a solid

25) When a wave is reflected from a rigid surface, it undergoes a phase change given by

A) 2

B) 4

C) D) 2

26) Two persons cannot hear each other on the surface of moon because the moon has

A) craters B) no atmosphere C) rocks which absorb sound D) dust suspended all around

27) The distance between two points differing in phase by 600 on a wave having velocity 360 ms-1

and frequency 500 Hz is A) 0.72 m B) 0.18 m C) 0.12 m D) 0.36 m

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28) A wave is given by the equation Y =10-4 sin (60t + 2x) where x and y are in meters and t in second, then wavelength of the wave is A) metre. B) 2 metre.

C) 2

3metre.

D) 3 metre.

29) Wavelength of ultrasonic waves in air is of the order of A) 1 cm B) 0.1 cm C) 10-4cm

D) 10-8 cm.

30) A string when stretched with a weight of 9 kg. weight produces a note of frequency 256 Hz. The weight required to produce an octave of the note is A) 36 kg wt. B) 9/4 kg wt. C) 18 kg wt. D) 4 kg wt.

31) When sound travels from air to water the quantity that remains unchanged is

A) speed B) frequency C) intensity D) wavelength

32) Beats can only be heard when the difference in frequencies is less than

A) 10 B) 20 C) 30 D) 100

33) Stationary waves of frequency 200 are formed in air. If velocity of the wave is 360m/s the shortest

distance between antinodes will be A) 1.8 m. B) 3.6 m. C) 2.7 m. D) 0.9 m.

34) A fork gives 5 beats with a 40 cm length of sonometer wire. If the length of the wire is shortened

by 1 cm, the number of beats is still the same. The frequency of the fork is A) 385 Hz B) 600 Hz C) 395 Hz D) 400 Hz

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35) A certain string will resonate to several frequencies, the lowest of which is 200 Hz. What are the next three higher frequencies to which it resonates A) 400,600,800 B) 100,200,300 C) 50,150,300 D) 200,250,300

36) A string of 0.3 m length is found to resonate in 3 segments (nodes at both ends) when the driving

frequency is 20 Hz. The speed of the wave in the string is A) 3 m/s B) 4 m/s C) 5 m/s D) 9 m/s

37) A wire of sonometer is 1m in length and has a fundamental frequency of 330Hz. The velocity of

transverse waves along the wire is A) 300 ms-1 B) 660 ms-1 C) 115 ms-1 D) 990 ms-1

38) The frequency of vibrating string is 200 Hz. If the tension is doubled, the frequency will be

approximately A) 400 Hz B) 280Hz C) 320 Hz D) 240 Hz

39) In open end organ pipe

A) only odd harmonics are produced B) only even harmonics are produced C) both odd and even harmonics are produced D) None of these

40) A man is watching two trains one leaving and other approaching with equal velocities of 4 ms-1. If

they sound their whistles each of natural frequency 240 Hz, the number of beats heard per sec by the man will be (velocity of sound in air 320 ms-1) A) 6 B) 12 C) 4 D) None of these

41) Speed of sound in air is 350 ms-1. An engine blows a whistle of frequency of 1200 Hz, it is

approaching the observer with velocity 50 ms-1. The apparent frequency as heard by the observer is A) 1600 Hz B) 1400 Hz C) 1050 Hz D) 300 Hz

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42) A motor cyclist moving at 30 km/hr blows a whistle of 476 Hz towards a cliff. If velocity of sound is 1220 km/hr, the apparent frequency of the echo heard by him is A) 250Hz B) 500 Hz C) 425 Hz D) 476 Hz

43) A stationary engine at a platform blows a whistle of frequency 305 vib/sec. If the velocity of

sound be 1220 km/hr, the frequency of the whistle as heard by a man running towards the engine with a speed of 20 km/hr is A) 300 vib/sec B) 305 vib/sec C) 310 vib/sec D) 320 vib/sec.

44) The wavelength of light coming from a star shifts towards the violet end of the spectrum.

This shows that the star is A) receding from the earth B) approaching the earth C) neither approaching nor receding from the earth D) sometimes approaching and sometimes receding from the earth

45) Ultrasonics are used for stirring liquid solutions in order to produce

A) soundless stirring B) perfectly homogeneous solution C) chemical reactions in them D) none of the above

46) A cylindrical tube with both ends open has fundamental frequency f in air. If the tube is vertically

dipped in water so that half of it is in water, the fundamental frequency is

A) 2f

B) 4

3 f

C) f D) 2 f

47) A star emitting light of 5000 Å is receding away from earth with a velocity of 300 km/s. The

apparent wavelength of light is A) 5000 Å B) 5005 Å C) 5050 Å D) 4095 Å

48) A wave of frequency 100 Hz travels along a string towards its fixed end. When this wave travels

back after reflection, a node is formed at a distance 10 cm from the fixed end. The speed of the wave (reflected and incident) is A) 5 ms-1 B) 20 ms-1 C) 100 ms-1 D) 40 ms-1

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49) Standing waves are produced in a 10 m long stretched string. If the string vibrates in 5 segments

and the wave velocity is 20m/s, the frequency is A) 2 Hz B) 4 Hz C) 5 Hz D) 10 Hz

50) Which one is not produced by sound waves in air? A) Polarisation B) Diffraction C) Refraction D) Reflection

51) The air column in a pipe which is closed at one end will be in resonance with a vibrating tuning

fork at a frequency 250 Hz, if the length of the air column is A) 33 cm. B) 62.5 cm. C) 45 cm. D) 12.5 cm.

52) An object producing a pitch of 1200 Hz is moving with a velocity of 40 m/s towards a stationary

person. The velocity of sound is 350m/s. The frequency of sound heard by stationary person is A) 700 Hz B) 1400 Hz C) 1050 Hz D) 1250 Hz

53) An unknown frequency x produces 8 beats per second with a frequency of 250Hz and 12 beats

with 270 Hz source, then x is A) 258 Hz B) 242 Hz C) 262 Hz D) none of these

54) If velocity of sound in air is 350 m/s then the fundamental frequency of a open pipe of length 50

cm is A) 175 Hz B) 350 Hz C) 700 Hz D) 500 Hz

55) An observer is watching two vehicles of same velocity ( 4 m/s). The former is approaching

towards the observer while the latter is receding. If the frequency of the siren of the vehicle is 240 Hz and velocity of sound in air is 320 m/s , then the beats produced is A) 6 B) 3 C) zero D) 12

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56) Which waves are used in sonography? A) Microwaves B) Infra-red waves C) Sound waves D) Ultrasonic waves

57) At what speed should a source of sound move so that observer finds that apparent frequency

equals to half of the original frequency?

A) 2

B) 2

C) 4

D)

58) The speed of sound in air is 333 m/s. The fundamental frequency of the open pipe is 333 Hz. The second overtone of the open organ pipe can be produced with a pipe of length A) 0.5 m B) 1.0 m C) 1.5 m D) 2.0 m

59) Two sound waves having a phase difference of 600 have path difference of

A) 21 B) ½ C) 1/6 D) 1/3

60) A tuning fork when sounded along with a standard source of frequency 300 Hz produces 5 beat /s.

The tuning fork when loaded by some wax is again found to give 5 beats/s with the standard source. The frequency of the fork originally was A) 290 Hz B) 295 Hz C) 305 Hz D) 310 Hz

61) If an open organ pipe is sounded with a tuning fork having frequency 256 Hz resonance occurrs at

35 cm and 105 cm, the velocity of sound is A) 360 m/s B) 512 m/s C) 524 m/s D) 720 m/s

62) Stationary waves of frequency 300 Hz are formed in a medium in which the velocity of sound is

1200 metre/second. The distance between a node and the neighbouring antinode is A) 1 m. B) 2 m. C) 3 m. D) 4 m.

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63) A stretched string resonates with tuning fork frequency 512 Hz when length of the string is 0.5 m. The length of the string required to vibrate resonantly with a tuning fork of frequency 256 Hz would be A) 0.25 m B) 0.5 m C) 1 m D) 2 m

64) A 5.5 m length of string has a mass of 0.035 kg. If the tension in the string is 77 N. The speed of a

wave on the string is A) 110 ms-1 B) 165 ms-1 C) 77 ms-1 D) 102 ms-1

65) When a wave travels in a medium, the particle displacements are given by

Y (x, t) = 0.03 sin (2t – 0.01 x) Where y and x expressed in metres and t in seconds . At a given instant of time, the phase difference between two particles 25 m apart is

A) 8

B) 4

C) 2

D)

66) Transverse wave of amplitude 0.1 m is generated at one end (x = 0) of a long string by a tuning fork of frequency 500 Hz. At a certain instant of time, the displacement of particle at x = 1.0 m is – 0.05 m and of particle at x = 2.0 m is + 0.05 m. How long does the wave take to travel from to ? A) 1 s

B) 101 s

C) 100

1 s

D) 1000

1 s

67) Transverse waves of the same frequency are generated in two steel wires and . The

diameter of is twice that of and the tension in is half that in B. The ratio of the velocities of waves in and is A) 1 : 2

B) 1 : 2

C) 1 : 2 2

D) 3 : 2 2

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68) Two parts of a sonometer wire, divided by a moveable knife – edge, differ in length by 1 cm and

produce 1 beat per second when sounded together. If the total length of the wire is 100 cm, the frequencies of the two parts of the wire are A) 51 Hz, 50 Hz B) 50.5 Hz, 49.5 Hz C) 49 Hz, 48 Hz D) 49.5 Hz, 48.5 Hz

69) A stone hangs from the free end of a sonometer wire whose vibrating length, when tuned to a

tuning fork, is 40 cm. When the stone hangs wholly immersed in water, the resonant length is reduced to 30 cm. The relative density of the stone is A) 16/9 B) 16/7 C) 16/5 D) 16/3

70) A cylindrical tube, open at both ends, has fundamental frequency n. If one of the ends is closed,

the fundamental frequency will become A) n /2 B) n C) 2 n D) 4 n

71) An organ pipe , open at both ends and another organ pipe, closed at one end, will resonate with

each other, if their lengths are in the ratio of A) 1 : 1 B) 1 : 4 C) 2 : 1 D) 1 : 2

72) Two loudspeakers A and B , 1.0 m apart, produce sound waves of the same wavelength and in the

same phase. A sensitive sound detector, moving along PQ, parallel to line AB, 2.4 m away, detects maximum sound at P ( on the perpendicular bisector of AB) and another maximum sound when it first reaches Q directly opposite to B, as shown in the figure. What is the wavelength of sound emitted by the speakers ? A) 0.1 m B) 0.2 m C) 0.3 m D) 0.4 m

A

1 m -------------------------------------------------------------------------- P

B Q

2.4 m

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73) A progressive wave in a medium is represented by the equation

Y = 0.1 sin 10 t - 115 x

where y and x are in cm and t in second. The maximum speed of a particle of the medium due to the waves is

A) 1 cm s-1 B) 10 cm s-1 C) (c) cm s-1 D) 10 cm s-1

74) A tuning fork of frequency 340 Hz is sounded above a cylindrical tube 1 m high. Water is slowly

poured into the tube. If the speed of sound is 340 m s-1, at what level of water in the tube will the sound of the fork be appreciably intensified ? A) 25 cm, 75 cm B) 20 cm, 80 cm C) 15 cm, 85 cm D) 17 cm, 83 cm

75) A sonometer wire, 65 cm long, is in resonance with a tuning fork of frequency . If the length of

the wire is decreased by 1 cm and it is vibrated with the same tuning fork, 8 beats are heard per second. What is the value of ? A) 256 Hz B) 384 Hz C) 480 Hz D) 512 Hz

76) Two organs pipes, each closed at one end, give 5 beats per second when emitting their

fundamental notes. If their lengths are in the ratio of 50 : 51, their fundamental frequencies (in Hz) are A) 250,255 B) 255,260 C) 260,265 D) 265,270

77) Two sources A and B are sounding notes of frequency 680 Hz. A listener moves from A to B with

a constant velocity u. If the speed of sound is 340 m s-1 , what must be the value of u so that he hears 10 beats per second ? A) 2.0 m s-1 B) 2.5 m s-1 C) 3.0 m s-1 D) 3.5 m s-1

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78) A uniform metal wire of density , cross sectional area A and length L is stretched with a tension T. The speed of transverse wave in the wire is given by

A) A

TL

B) ALT

C) A

T

D) A

T

79) A pipe of length 20 cm is closed at one end. Which harmonic mode of the pipe is resonantly excited by a 425 Hz source ? The speed of sound = 340 m s-1 A) First harmonic B) Second harmonic C) Third harmonic D) Fourth harmonic

80) A pipe of length 20 cm is open at both ends. Which harmonic mode of the pipe is resonantly

excited by a 1700 Hz source ? The speed of sound = 340 m s-1 A) First harmonic B) Second harmonic C) Third harmonic D) Fourth harmonic

81) Two tuning forks A and B produce 10 beats per second when sounded together. On slightly

loading fork A with a little wax, it was observed that 15 beats are heard per second. If the frequency of fork B is 480 Hz. What is the frequency of fork A before u was loaded ? A) 465 Hz B) 470 Hz C) 490 Hz D) 495 Hz

82) Two sitar strings A and B are slightly out of tune and produce beats of frequency 6 Hz. When the

tension in string A is slightly decreased, the beats frequency is found to be reduced to 3 Hz. If the original frequency of A is 324 Hz, what is the frequency of B? A) 318 Hz B) 321 Hz C) 327 Hz D) 330 Hz

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83) A metal wire of diameter 1 mm is held on two knife edges separated by a distance of 50 cm. The tension in the wire is 100 N. The wire vibrating with its fundamental frequency and a vibrating tuning fork together produce 5 beats per second. The tension in the wire is then reduced to 81 N. When the two are excited, beats are heard at the same rate. What is the frequency of the fork? A) 90 Hz B) 95 Hz C) 100 Hz D) 105 Hz

84) An ambulance blowing a siren of frequency 700 Hz is traveling slowly towards a vertical

reflecting wall with a speed of 2 m s-1. The speed of sound is 350 m s-1. How many beats are heard per second? A) 4 B) 6 C) 8 D) 10

85) Two persons A and B, each carrying a source of sound of frequency n, are standing a few metres

apart in a quiet field. A starts moving towards B with a speed u. If v is the speed of sound, the number of beats heard per second by A will be

A) nu

B) nu2

C) )( uv

nu

D) )( uv

nu

86) A train standing at a certain distance from a railway platform is blowing a whistle of frequency

500 Hz. If the speed of sound is 340 m s-1 , the frequency and wavelength of the sound of the whistle heard by a man running towards the engine with a speed of 10 m s-1 respectively are A) 500 Hz, 0.7 m B) 500 Hz, 0.68 m C) 486 Hz, 0.7 m D) 515 Hz, 0.68 m

87) A submarine is fitted with a SONAR (SOund Navigation And Ranging) system which operates at

an ultrasonic frequency of 42 KHz. An enemy submarine is moving towards the SONAR with a speed of 200 m s-1. If the speed of sound in seawater is 1400 m s-1 , what is the frequency of sound received back at the SONAR fitted submarine after reflection from the enemy submarine ? A) 36 KHz B) 42 KHz C) 48 KHz D) 56 KHz

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88) A machine gun is mounted on a tank moving at a speed of 20 m s-1 towards a target with the gun pointing in the direction of motion of the tank. The muzzle speed of the bullet equals the speed of sound = 340 m s-1 . If , at the time of firing , the target is 500 m away from the tank, then A) The sound arrives at the target later than the bullet B) The sound arrives at the target earlier than the bullet C) Both sound and bullet arrive at the target at the same time D) The bullet will never arrive at the target

89) When a wave travels in a medium, the particle displacements are given by

Y = a sin 2 (bt – cx) Where a, b and c are constants. The maximum particle velocity will be twice the wave velocity if

A) c = a1

B) c = a C) b = ac

D) b = ac1

90) Three sound waves of equal amplitudes have frequencies (v-1), (v) and (v+1). They superpose to

give beats. The number of beats produced per second will be A) v

B) 2v

C) 2 D) 1

91) Nine tuning forks are arranged in order of increasing frequency. Each tuning fork produces 4 beats

per second when sounded with either of its neighbours. If the frequency of the 9th tuning fork is twice that of the first, what is the frequency of the first tuning fork? A) 32 Hz B) 40 Hz C) 48 Hz D) 56 Hz

92) A sonometer wire of length 120 cm is divided into three segments of lengths in the ratio of

1: 2 : 3. What is the ratio of their fundamental frequencies? A) 3 : 2 : 1 B) 4 : 2 : 1 C) 5 : 3 : 2 D) 6 : 3 : 2

93) A tuning fork produces 4 beats per second when sounded with a sonometer wire of vibrating

length 48 cm. It produces 4 beats per second also when the vibrating length is 50 cm. What is the frequency of the tuning fork? A) 196 Hz B) 284 Hz C) 375 Hz D) 460 Hz

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94) Two identical strings of a stringed musical instrument are in unison when stretched with the same tension. When the tension in one string is increased by 1 %, the musician hears 4 beats per second. What was the frequency of the note when the strings were in unison? A) 796 Hz B) 800 Hz C) 804 Hz D) 808 Hz

95) The wavelength of light of a particular wavelength received from a galaxy is measured on earth

and is found to be 5 % more than its actual wavelength. It follows that the galaxy is A) approaching the earth with a speed 3 107 m s-1 B) going away from the earth with a speed 3 107 m s-1 C) approaching the earth with a speed 1.5 107 m s-1 D) going away from the earth with a speed 1.5 107 m s-1

96) Radiowaves of frequency 600 MHz are sent by a radar towards an enemy aircraft. The frequency

of the radiowaves reflected from the aircraft as measured at the radar station is found to increase by 6KHz. It follows that the aircraft is A) approaching the radar station with a speed 1.5 kms-1 B) going away from the radar station with a speed 1.5 k ms-1 C) approaching the radar station with a speed 3 k ms-1 D) going away from the radar station with a speed 3 k ms-1

97) An observer moves towards a stationary source of sound with a velocity one-tenth the velocity of

sound. The apparent increase in frequency is A) zero B) 5 % C) 10 % D) 0.1 %

98) Two wires of the same material and radii r and 2r are welded together end to end. The

combination is used as a sonometer wire and kept under tension T. The welded point is mid-way between the two bridges. When stationary waves are set up in the composite wire, the joint is a node. Then the ratio of the number of loops formed in the thinner to thicker wire is A) 2 : 3 B) 1 : 2 C) 2 : 1 D) 5 : 4

99) A uniform rope of length 12 m and mass 6 kg hangs vertically from a rigid support. A blocks of

mass 2 kg is attached to the free end of the rope. A transverse pulse of wavelength 0.06 m is produced in the lower end of the rope. What is the wavelength of the pulse when it reaches the top of the rope? A) 0.06 m B) 0.03 m C) 0.12 m D) 0.09 m

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100) A tube closed at one end containing air, produces when excited, the fundamental note of frequency 512 Hz. If the tube is open at both ends, the fundamental frequency that can be excited is (in Hz) A) 1024 B) 512 C) 256 D) 128

101) Two sound waves of equal intensity I produce beats. The maximum intensity of sound produced in

beats will be A) I B) 4 I C) 2I D) I/2

102) A train blowing its whistle moves with a constant velocity u away from the observer on the

ground. The ratio of the actual frequency of the whistle to that measured by the observer is found to be 1.2. If the train is at rest and the observer moves away from it at the same velocity, the ratio would be given by A) 0.51 B) 1.25 C) 1.52 D) 2.05

103) An organ pipe P1,closed at one end vibrating in its first harmonic and another pipe P2 open at both

ends vibrating in its third harmonic, are in resonance with a given tuning fork. The ratio of the length of P1 and P2 is

A) 38

B) 61

C) 21

D) 31

104) A traveling wave in a stretched string is described by the equation.

Y = A sin (kx - t) The maximum particle velocity is

A) A

B) k

C) dkd

D) tx

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105) Two vibrating strings of the same material but lengths L and 2L have radii 2r and r respectively. They are stretched under the same tension. Both the strings vibrate in their fundamental modes, the one of length L with frequency 1 and the other with frequency 2. The ratio 1/ 2 is given by A) 2 B) 4 C) 8 D) 1

106) Two sounds of wavelengths 5 m and 6 m, traveling in a medium produce 10 beats per second. The

speed of sound in the medium is A) 300 ms-1 B) 320 ms-1 C) 350 ms-1 D) 1200 ms-1

107) The frequencies of tuning forks A and B are respectively 3 % more and 2 % less than the

frequency of fork C. When A and B are simultaneously excited, 5 beats per second are produced. The frequency (in Hz) of fork A is A) 98 B) 100 C) 103 D) 105

108) A radar sends a radio signal of frequency 9 x 109 Hz towards an aircraft approaching the radar. If

the reflected wave shows a frequency shift of 3 x 10 3 Hz, the speed with which the aircraft is approaching the radar is (velocity of radio signal is 3 x 10 8 ms-1) A) 150 ms-1 B) 100 ms-1 C) 50 ms-1 D) 250 ms-1

109) A progressive wave of frequency 500 Hz is traveling with a velocity of 360 m/s. How far are two points 600 out of phase? A) 0.06 m B) 0.12 m C) 0.18 m D) 0.24 m

110) An aluminium wire of length 60 cm is joined to a steel wire of length 80 cm and stretched between two fixed supports. The tension produced is 40 N. The cross sectional area is 1 mm2 for the steel wire and 3 mm 2 for the aluminium wire. The minimum frequency of the tuning fork which can produce standing waves with the joint as node is A) 90 Hz B) 145 Hz C) 180Hz D) 250 Hz

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111) A sonometer wire resonates with a given tuning fork and forms a standing wave with 5 antinodes between two bridges when a 9 kg weight is suspended from the wire. When the mass is replaced by a mass M, the wire resonates with the same tuning fork forming 3 antinodes for the same position of wedges. The value of M is A) 2.25 kg B) 5 kg C) 12.5 kg D) 25 kg

112) The velocity of sound in air is 330 m/s. The velocity of sound in vacuum is A) 332 m/s B) 330 m/s C) 288 m/s D) zero

113) The number of beats produced per second by two tuning forks sounded together is 4. One of them has a frequency of 250 Hz. The frequency of the other cannot be less than A) 254 Hz B) 252 Hz C) 248 Hz D) 246 Hz

114) The first resonance length in a closed organ pipe is 50 cm. The second resonance length will be A) 50 cm B) 100 cm C) 150 cm D) 200 cm

115) The speed of a supersonic wave as compared to that of sound is A) less B) more C) equal D) 1/10

116) A resonance tube is resonated with a tuning fork of frequency 256 Hz. If the length of resonating air columns are 32 cm and 100 cm, then end correction will be A) 1 cm B) 2 cm C) 4 cm D) 6 cm

117) The vibrations in the stem of tuning fork are A) transverse B) longitudinal C) both transverse and longitudinal D) none of these

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118) The fundamental frequency in a stretched string is 100 Hz. To double the frequency, the tension in it must be changed to A) T2 = 2 T1 B) T2 = 4T1 C) T2 = T1 D) T2 = T1/4

119) The frequency of an open pipe is 300 Hz. The first overtone of this pipe is the same as the second overtone of a closed pipe. The length of the closed organ pipe is A) 11 cm B) 21 cm C) 42 cm D) 84 cm

120) The sound box of a sonometer increases A) speed of sound B) intensity of sound C) wavelength of sound D) frequency of sound

121) The speed of sound in air is 320 m/s. The length of a closed pipe is 1 m. Neglecting the end correction, the resonant frequency for the pipe will be A) 80 Hz B) 240 Hz C) 320 Hz D) 400 Hz

. 122) On increasing the distance between the source of sound and the observer by three times, the

intensity of sound becomes A) 9 B) 3 C) 1/3 D) 1/9

123) The total mass of a sonometer wire remains constant. On increasing the distance between the two bridges by four times, its frequency will become A) 0.25 times B) 0.5 times C) 2 times D) 4 times

124) If the equations of two sound waves are y1 = 5 sin 252 t and y2 = 5 sin 280 t respectively, the number of beats heard per second will be A) 34 B) 12 C) 6 D) 0

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125) The second overtone of a closed organ pipe P1 and the third overtone of an open pipe P2 are in unison with a tuning fork. The ratio of the length of P1 to P2 will be A) 8 : 3 B) 3 : 8 C) 3 : 1 D) 1 : 3.

126) Two open pipes, whose lengths are 50 cm and 51 cm respectively, produce five beats per second when sounded together. The fundamental frequencies in hertz will be A) 65 and 60 B) 90 and 95 C) 245 and 250 D) 255 and 250.

127) A resonance tube of diameter 2 cm is vibrating in unison with a tuning fork of frequency 512 Hz. When the length of air column above water level is 13.5 cm, the wavelength of the note will be A) 31.0 cm B) 32.2 cm C) 54 cm D) 62.0 cm

128) A wave y = 10 sin (200 t - 0.5 x) travels in space. The separation between two rarefactions is A) 2 cm B) 10 cm C) 2 π cm D) 4 π cm

129) A sitar wire vibrates with frequency of 330 vibrations per second. If its length is increased three times and tension is increased four times then the frequency of the wire will be A) 110 Hz B) 220 Hz C) 330 Hz D) 440 Hz

130) An organ pipe P1 closed at one end vibrating in its first harmonic and pipe P2 open at both ends vibrating in its third harmonic are in resonance with the same tuning fork. The ratio of their lengths is A) 3/4 B) 3/8 C) 1/8 D) 1/6

131) The frequency of the first overtone of an open organ pipe is f , then that of the closed organ pipe will be A) 3 f /4 B) f C) f /2 D) f /4

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132) A rod 70 cm long is damped at the middle. The velocity of sound in the material of the rod is 3500 m/s. The frequency of fundamental note produced by it is A) 3500 Hz B) 2500 Hz C) 1250 Hz D) 700 Hz

133) The tension in a wire is decreased by 19 %. The percentage decrease in frequency will be A) 10 % B) 19 % C) 0.19 % D) 9 %

134) An open organ pipe of length 50 cm vibrates in unison with a tuning fork of frequency f. The diameter of the pipe is 3 cm. The wavelength of the note produced is A) 204 cm B) 102 cm C) 96 cm D) 51 cm

135) A boat at anchor is rocked by a wave whose crests are 100 m apart and whose velocity is 0.25 m/s. These waves reach the boat once every A) 2500 s B) 1500 s C) 4 s D) 0.25 s

136) A tuning fork of frequency 290Hz appears to be vibrating with a frequency of 10 Hz when observed in a flashing illumination. The frequency of the flashing light is A) 10 Hz B) 270 Hz C) 280 Hz D) 290 Hz

137) For a resonance tube the air columns for the first and the second resonance differ in length by 31.5 cm. The wavelength of the sound wave is A) 252 cm B) 126 cm C) 63 cm D) 31.5 cm

138) If one of the prongs of a tuning fork is broken, then its frequency of vibration A) remains the same B) decreases C) increases D) becomes zero

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139) Two tuning forks when sounded together produce 6 beats per second. The first fork has a frequency 3 % higher than a standard fork and the second fork has a frequency 2 % lower than the same standard fork. The frequencies for the forks are A) 126.3 & 120.3 Hz B) 162.7 & 156.7 Hz C) 136.2 & 130.2 Hz D) 123.6 & 117.6 Hz

140) An air column closed at one end and open at the other end resonates with a tuning fork at 45 cm

and 99 cm of length. The wavelength of sound in the air column is A) 36 cm B) 54 cm C) 108 cm D) 180 cm

141) The frequency of a tuning fork is 384 Hz and velocity of sound in air is 352 m/s. After 36 vibrations of the fork, the sound will travel a distance of A) 11 m B) 22 m C) 33 m D) 16.5 m

142) An open pipe is suddenly closed at one end. As a result the frequency of third harmonic of the closed pipe is found to be higher by 100 Hz. The fundamental frequency of the open pipe is A) 200 Hz B) 30 Hz C) 240 Hz D) 480 Hz

143) Two successive resonance frequencies in an open organ pipe are 1944 and 2592 Hz. The speed of sound in air is 324 m/s. Then length of the pipe is A) 12.5 cm B) 25 cm C) 50 cm D) 100 cm

144) A source of sound emits a note of 1200 Hz which travels along a straight line at a speed of 170 m/s. A detector is placed at a distance of 200 cm from the line of motion of the source. The velocity of sound is 340 m/s. The frequency of the sound received by the detector when it is closest is A) 800 Hz B) 1600 Hz C) 2400 Hz D) 3200 Hz

145) A driver of a car approaching a vertical wall notices that the frequency of his car horn has changed

from 440 to 480 Hz, when it gets reflected from the wall. If the speed of sound is 330 m/s, the speed of the car will be A) 16.3 m/s B) 15.3 m/s C) 14.3 m/s D) 13.3 m/s

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146) When both source and listener move in the same direction with a velocity equal to half the velocity of sound the change in the frequency of sound as detected by the listener is A) 100 % B) 50 % C) 25 % D) zero

147) The wavelength of the sound produced by a source is 0.8 m. Velocity of sound is 320 m/s. If the source moves towards the stationary listener at 32 m/s, the apparent wavelength of the sound is A) 0.80 m B) 0.72 m C) 0.40 m D) 0.36 m

148) The velocity of sound in air is 330 m/s. To increase the apparent frequency of the sound by 50 %, the source should move towards the stationary source with a velocity of A) 55 m/s B) 110 m/s C) 220 m/s D) 330 m/s

149) A train is approaching the platform with a speed of 4 m/s. Another train is leaving the platform with the same speed. The velocity of sound is 320 m/s. If both the trains sound their whistles at frequency 230Hz, the number of beats heard per second will be A) 9 B) 8 C) 7 D) 6

150) A pendulum vibrates with a time period of 1 second. The sound produced by it is in the A) audible range B) infrasonic range C) ultrasonic range D) supersonic range

151) Beats are the result of A) constructive and destructive interference in time B) constructive and destructive interference in space C) destructive interference in space D) constructive interference in space

152) A star is receding away from the earth with a velocity of 105 m/s. If the wavelength of its spectral

line is 5700 Å, then the Doppler shift will be A) 0.2 Å B) 1.9 Å C) 20 Å D) 38 Å

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153) A rocket is receding away from the earth with velocity 0.2c. The rocket emits a signal of frequency 4 107 Hz. The apparent frequency of the signal produced by the rocket observed by the observer on earth will be A) 2.8 107 Hz B) 4 107 Hz C) 3.2 107 Hz D) 4.5 107 Hz

154) A car is moving towards a person. The person observes a change of 2.5 % in the frequency of its horn. If the velocity of sound is 320 m/s, then the velocity of the car is A) 6 m/s B) 8 m/s C) 10 m/s D) 12 m/s

155) An ultrasonic scanner is used in a hospital to detect tumor in tissues. The working frequency of the scanner is 4.2 mega Hz. The velocity of sound in the tissue is 1.7 km/s. The wavelength of sound in the tissue is nearest to. A) 4 10-3 B) 8 10-3 m C) 4 10-4 m D) 8 10-4 m

156) Surface waves strikes the rock with their crests 160 m apart. The velocity of the waves is 40 m/s. The time interval between two crests striking the rock is A) 8 s B) 4 s C) 2 s D) 1 s

157) When you speak to your friend, which of the following quantities have a unique value in the sound produced? A) amplitude B) wave velocity C) frequency D) wave length

158) A person places his ear at the end of a long steel pipe. He hears two distinct sounds at an interval of 0.5s when another person hammers at the other end of the pipe. If the speed of sound in the metal and air are 3630 m/s and 330 m/s respectively, then the distance between the two persons is A) 90.75 m B) 181.5 m C) 363 m D) 1650 m

159) Through a progressive wave

A) Energy is transferred by the transfer of medium B) Energy need not be transferred C) Energy is transferred from one point to another without the actual transfer of medium

particles D) Energy is transferred by transfer of particle

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160) In a stationary wave A) Particle constituting the wave remains stationary B) Maxima and minima do not change their position C) Amplitude is fixed D) Frequency of wave is zero

161) A point source emits waves in all directions in a non-absorbing medium. The ratio of the

amplitudes of waves at two points at distances 9 and 25 m from the source is A) 9:25 B) 25:9 C) 3:5 D) 5:3

162) A sound wave of frequency 256 Hz travels at 330 m/s through air. At what speed does a sound

wave of frequency 512 Hz travels through the same air A) 165 m/s B) 330 m/s C) 660 m/s D) 1320 m/s

163) A wire of length 5 m has a linear density of 4 10-3 kg/cm. It is fixed at one end. A tension of 102

N is applied to the other end. A disturbance is produced at one end. The time taken by the disturbance to reach the other end is

A) s)10(

B) 1/ s)10(

C) 1/10 s)10(

D) 1/5 s)10(

164) A certain broadcasting station broadcasts at a frequency of 12 megahertz. The speed of radio waves is 3 108 m/sec. The wavelength of the waves transmitted by station is A) 25 m B) 2.5 m C) 36 m D) 3.6 m

165) The wavelength of sound from a tuning fork of frequency 330 hertz is nearly

A) 100 cm B) 10 cm C) 1 cm D) 330 cm

166) Sound waves of frequency 660 Hz fall normally on a perfectly reflecting wall. The shortest distance from the wall, at which air particles have maximum amplitude of vibration is A) 0.5 m B) 0.25 m C) 0.125 m D) 0.0625 m

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167) Which of the following equations represents a simple harmonic progressive wave? A) Y = a sin ( t ) B) Y = a sin t cos kx C) Y = a sin ( kxt ) D) Y = a cos t

168) When a longitudinal wave propagates through air, the instantaneous acceleration of the particle is proportional to its A) Frequency B) Displacement C) Velocity D) None of these

169) When a tuning fork is made to vibrate, then the vibrations of its prongs A) Are in phase B) Have a phase difference of C) Have a phase difference of 2/ D) Have a phase difference of 4/

170) A thunder clap is heard 5.5 sec later than the lightning flash. The distance of the flash is (velocity of sound in air is 330 m/s) A) 1780 m B) 1815 m C) 3560 m D) 300 m

171) The equation of a plane progressive wave is y = 8 sin (0.02x - 4.00t) where y and x are given in cm and time t is in seconds, the speed of wave is A) 100 cm/sec B) 200 cm/sec C) 2 cm /sec D) 50 cm/sec

172) Energy is not carried by A) Mechanical elastic waves B) Longitudinal waves C) Transverse waves D) Stationary waves

173) A bat emits ultrasonic waves of frequency of 39 kHz and receives an echo 0.2 sec later. If the speed of sound in air is 300 m/s and the speed of electromagnetic waves 3 102 m/s then the distance of the bat from the object producing the echo is A) 60 m B) 30 m C) 3 107 m D) 3 106 m

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174) The vibrations taking place in diaphragm of microphone will be A) Free vibrations B) Damped vibrations C) Forced vibrations D) Electrically maintained vibrations

175) A wire having a linear density of 0.05 g/cm is stretched between two rigid supports with a tension of 4.5 102 N. It is observed that the wire resonates at a frequency of 420 Hz. The next higher frequency at which the wire resonates is 490 Hz. The length of the wire is A) 2.14 m B) 6.43 m C) 21.4 m D) 64.28 m

176) The wavelengths of two notes in air are 72/195 m and 72/193 m. Each note produces 5 beats per second with a third note of a fixed frequency. The velocity of sound in air is A) 180 m/s B) 240 m/s C) 360 m/s D) 420 m/s

177) A set of 65 tuning forks is so arranged that each gives 3 beats per second with the preceding one. If the last fork is the octave of the first, the frequencies of the first and the last fork are A) 96 Hz, 192 Hz B) 99 Hz, 198 Hz C) 192 Hz, 384 Hz D) 198 Hz, 396 Hz

178) An engine approaches a hill with a constant speed. When it is at a distance of 0.9 km it blows a whistle, whose echo is heard by the driver after 5 seconds. If the speed of sound in air is 330 m/s, the speed of the engine must be A) 15 m/s B) 30 m/s C) 60 m/s D) 90 m/s

179) The wavelength of the light coming from a distant galaxy is found to be 5 % more than that coming from a source on earth. The speed of recession of galaxy is A) 0.5 106 m/s B) 1.5 106 m/s C) 3.15 106 m/s D) 6 106 m/s

180) A stone is dropped into a well and its splash is heard at the mouth of the well after an interval of 1.45 seconds. Velocity of sound is 332 m/s. The depth of the well is A) 4.45 m B) 6.6 m C) 9.9 m D) 16.5 m

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181) Two identical sonometer wires have a fundamental frequency of 500 Hz, when kept under the same tension. Both wires are made to vibrate together. The fractional increase in the tension that would cause an occurrence of 5 beats per second is A) 0.5 % B) 1.0 % C) 1.5 % D) 2.0 %

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5. WAVE MOTION & SOUND

Ques. No. Answer 1 C

2 C

3 B

4 A

5 B

6 C

7 B

8 B

9 A

10 D

11 D

12 A

13 C

14 A

15 A

16 B

17 D

18 D

19 A

20 C

21 C

22 D

23 B

24 C

25 C

26 B

27 C

28 A

29 A

30 A

31 B

32 A

33 D

34 C

35 A

36 B

37 B

38 B

39 C

40 A

41 B

42 B

43 C

Ques. No. Answer 44 B

45 B

46 C

47 B

48 B

49 C

50 A

51 A

52 B

53 A

54 B

55 A

56 D

57 D

58 D

59 C

60 C

61 A

62 A

63 C

64 A

65 B

66 D

67 C

68 B

69 B

70 A

71 C

72 B

73 C

74 A

75 D

76 A

77 B

78 C

79 A

80 B

81 B

82 A

83 B

84 C

85 A

86 D

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Ques. No. Answer 87 D

88 A

89 A

90 D

91 A

92 D

93 A

94 B

95 D

96 A

97 C

98 B

99 B

100 A

101 B

102 B

103 B

104 A

105 D

106 A

107 C

108 C

109 B

110 C

111 A

112 D

113 D

114 C

115 B

116 B

117 B

118 B

119 C

120 B

121 A

122 D

123 A

124 D

125 B

126 D

127 C

128 D

129 C

130 D

131 A

Ques. No. Answer 132 B

133 A

134 B

135 C

136 C

137 C

138 A

139 D

140 C

141 C

142 A

143 B

144 B

145 C

146 D

147 B

148 B

149 C

150 B

151 B

152 B

153 C

154 B

155 C

156 B

157 B

158 B

159 C

160 B

161 B

162 B

163 B

164 A

165 A

166 C

167 C

168 B

169 B

170 B

171 B

172 D

173 B

174 C

175 A

176 C

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Ques. No. Answer 177 C

178 B

179 B

180 C

181 D

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