Physics XI Karachi Board MCQs Chapter 8

Chapter 8 - Wave Motion and Sound
1. If k is a positive constant __________ of the following expression represents simple harmonic motion (x is the displacement of particle from mean position).

(Acceleration = kx, acceleration = -kx, acceleration = kx2, acceleration = -kx2)

2. If k and a are the positive constants and x is the displacement from equilibrium position. __________ of the following expression represents S.H.M.

(Velocity = k (a2-x2), Velocity = Ök(a2 – x2),Velocity =Ök(x2 – a2), Velocity = k(x2-a2))

3. A bob of mass m is hanging from the end of an elastic spring and executing S.H.M with a period T. If this mass is replaced by another bob of mass 2m, the new time period of this system will be __________.

(T, 2T, Ö2T, T/2)

4. A bob of mass m is hanging from the end of an inelastic string is executing S.H.M with a period T. If this bob is replaced by an other bob of double mass. The new time period of this system will be __________.

(T, 2T, Ö2T, T/2)

5. __________ of is not true for S.H.M.

(Motion is Periodic, Elastic Restoring force must be present, System may possess inertia, Total Energy of system is conserved)

6. A body is attached to the end of a spring is executing S.H.M. at the extreme position its __________.




(Kinetic energy is maximum, Kinetic Energy is zero, Both kinetic and potential energy are zero, its velocity is maximum)

7. The motion of the simple pendulum is __________.

(Always simple harmonic, may be simple harmonic, can never be simple harmonic, circular)

8. A body is executing S.H.M if __________.

(Its acceleration is proportional to displacement and directed away from mean postion, Its acceleration is proportional to displacement and directed towards mean position, Its acceleration is zero, none of these)

9. A body is executing S.H.M at the mean position if __________.

(If its acceleration is maximum, its acceleration is zero, its velocity is zero, it posseses maximum potential energy)

10. A body is executing S.H.M at the mean position if __________.

(Its acceleration is maximum, Its velocity is maximum, It possesses maximum potential energy, none of these)

11. A body is executing S.H.M if __________.

(Its amplitude of motion remains constant, Its amplitude of motion may be constant, Its motion is not periodic, its motion may be vibratory)

12. A body is executing S.H.M with force constant k with an amplitude ‘a’, when its displacement is ‘x’. Its instantaneous K.E is represented by __________.

(1/2 k(x2-a2), ½ kx2, ½ k(a2-x2), A(k/m)

13. A simple pendulum is performing S.H.M with period T. If its length is doubled. The new time period will be __________.

(2T, 0.5T, 2.5T, 1.414 T)

14. If we increase the length of simple pendulum its time period will __________.

(Increase, Decrease, Remain same, becomes infinite)

15. A simple pendulum that behaves as a seconds pendulum on earth. If it is taken to moon. Where gravitational acceleration is one sixth that on earth. Its time period will become __________.

(4seconds, 12seconds, 3.5 seconds, 4.9 seconds)

16. A particle is moving in a circular path with constant angular speed. The motion of its projection along its any diameter is __________.

(Projectile, Translatory, Vibratory, Circular)

17. The trajectory of the bob of a vibrating simple pendulum after it has got suddenly detached from the thread while passing through its mean position is __________.

(Straight Line, Circular, Parabolic, Hyperbolic)

18. A string stretched between two fixed points is vibrating in one segment. The frequency generated is called __________.

(First overtone, fundamental Frequency, Second Harmonic, Normal Harmonic)

19. When the temperature of air rises, the speed of sound waves increases because.

(Frequency of the wave increases, both frequency and wavelength increases, Only wave length increases, Neither frequency nor wavelength changes)

20. The angular speed of the second hand of a watch is __________.

(p/30 rad/s, 1 rad/s, prad/s, 2p rad/s)

21. Restoring force is always present in __________.

(Linear Motion, Circular Motion, Simple Harmonic Motion, Projectile Motion)

22. The frequency of vibration in string of sonometer under tension T is f. If the vibrating length is halved, keeping tension constant, for the same wire, the frequency becomes __________.

(2f, 12f, ½ f, 4f)

23. A simple pendulum is transported to moon its frequency of oscillation will __________.

(Decreases, Increases, Remain constant, Become zero)

24. The pitch of note obtained by plucking a stretched string would be lowered by __________.

(Increasing the tension of the wire, Plucking it more vigorously, reducing the length of the string, wrapping a length of the fine wire round the string)

25. When pitch of a note is raised then __________.

(Frequency is decreased, Speed of sound is increased,

speed of sound is decreased, wavelength is increased)




26. __________ of the following must differ for a transverse and longitudinal wave moving in the same direction.

(Wavelength, Frequency, Amplitude, direction of Vibration)

27. A spectator watching a cricket match sees the bat strikes the ball and hears the sound of this about half a second later. This is because light waves and sounds waves have a different __________.

(Amplitude, Frequency, Intensity, Speed)

28. In one medium a wave has a frequency of the wave length l and speed c, the waves passes from this medium to another where its speed is 2/3c. In the second medium the __________.

(frequency is still f and the wave length still l, frequency is still f, but wavelength is 2/3 l, the wavelength is still l, but frequency is 2/3f, frequency is still f, but wavelenth is 3/2 l)

29. Dolphins can communicate by emitting sounds of frequency 150,000 Hz. If speed of sound in water is 1500 m/s, the wavelength of these sounds will be __________.

(1 m, 0.1 m, 0.01 m, 0.001m)

30. The motion of the particles of air, when sound waves passes through it is __________.

(Period, Circular, Is an example of Brownian motion, Motion will constant acceleration)

31. Two stringed instruments are playing notes of the same pitch, __________ of the following must be same for these notes.

(Amplitude, Frequency, Length of String, quality)

32. A simple pendulum is performing simple harmonic motion (SHM) __________ of the following will remain constant through out its motion.

(Acceleration of the bob, Its amplitude, Force on the bob, Velocity of the bob)

33. For a system to execute S.H.M, its must possesses __________.

(Only elasticity, Only inertia, Elasticity as well as inertia, Neither elasticity nor inertia)

34. A spring of force constant k is broken into two equal parts, then the force constant of each part is __________.

(k/2, 2k, k/Ö2, k)

35. The SI unit for force constant are __________.

(N, Nm-1, Nm-2,Nm)

36. Time period of a simple pendulum is T. It is kept in a lift, which is accelerating upward. The time period of the pendulum will __________.

(Increase, Decrease, Remain the same, First increase then decrease)

37. In the above question if the lift moves upwards with uniform velocity, its time period will __________.

(Increases, Decreases, Remain the same, Nothing can be said)

38. In the question number 36, the lift falls freely. They the time period will __________.

(Increase, Decrease, Remain the same, Become infinite)

39. A body is executing S.H.M of amplitude A. Its potential energy is maximum when it displacement is __________.

(Zero, A/2, A, ±A)

40. Mass m is suspended from an elastic spring of spring constant k. The time period of small oscillation is __________.

(2p Öm/k, 2p Ö2m/k, 2p Ök/m, 2p Ö2k/m)

41. The dimensional formula for spring constant k is __________.

(MT-3, MT-2, MLT-2MT-1)

42. In resonance condition the amplitude of oscillation is __________.

(Very small, Small, Very large, Large)

43. The SI unit of force constant is identical to that of __________.

(Pressure, Energy, Surface Tension, Force)

44. If the oscillations are highly damped, the amplitude of oscillation __________.

(Decreases with time, Increases with time, Remains constant with time, First increases then decreases)

45. The time period of a simple pendulum at the centre of the earth is __________.

(Zero, Infinity, Unity, Same as thaht at the surface of the earth)

46. In S.H.M the maximum acceleration is a and maximum velocity is b, its time period is __________.

(2pb/a, 2pa/b, a/2pb, b/2pa)

47. In S.H.M the graph between force and displacement is __________.

(Parabolic, Hyperbolic, Exponential, Linear)

48. The tuning fork A is of a slightly higher frequency than a fork B. they are employed to produce beats. On loading the fork A the frequency of beats will __________.

(Increase, Decrease, Remain the same, become zero)

49. Beats are the result of __________.

(Diffraction, Constructive Interference only, Destructive Interference only, Constructive and Destructive Interference both)

50. The distance between two consecutive nodes of a stationary wave is __________.

(l, l/2, l/4, l/6)

51. The stem of a vibrating tuning fork is pressed against a tabletop. The duration of its vibration __________.

(Increase, Decrease, Remains unchanged, Becomes infinite)

52. In a simple harmonic motion we have the conservation of __________.

(Kinetic energy, Potential energy, Total energy, Electrical energy)

53. The velocity of longitudinal vibrations in a solid depends on its __________.

(Rigidity Modulus, Bulk Modulus, Young’s Modulus, Poison’s Ratio)

54. In a simple harmonic motion __________ is constant.

(K.E is constant, amplitude is constant, phase is constant, P.E is constant)

55. When beats are produced by two travelling waves of nearly the same frequency then __________.

(the particles vibrate simple harmonically with a frequency equal to the difference in the frequencies of the two waves, the amplitude of vibration at any point changes simple harmonically with a frequency equal to the difference in the frequencies of the two waves, The frequency of beats depends on the position, where the beats are heard, the frequency of beats decreases as the time is passing_

56. When beats are produced by two travelling waves of same amplitude and of nearly the same frequencies, then __________.

(The maximum loudness heard is two times thaht corresponding to each of the constituent waves, The amximum loudness heard is four times thaht corresponding to each of the constituent waves, The maximum loudness heard is the same as thaht of corresponding to each of the constituent waves, the maximum loudness heard is 8 times thath corresponding to each of the wave)

57. When beats are produced by two waves, T1 = a sin 1000pt and T2 = a sin 1008 pt then __________ of the following gives the frequency of the beats heard.

(8p/sec, 8 /sec, 4/sec, 4p/sec)

58. When stationary waves are set up in a medium, __________ of the following statements is correct.

(Rarefaction occurs at the antinode, Compression takes place at all the nodes, no strain is felt at the antinodes, Maximum strain is felt at the antinodes)

59. When stationary waves are set then __________.

(All the particles of the medium are in same phase, particles separated by a distance of an amplitude out of phase, all the particles between two consective nodes are in phase, particles separated by a distance of an amplitude are always in phase)

60. When stationary waves are set up in a medium then __________.

(Energy is propagated at a rate double thaht of travelling waves of equal amplitude and of equal velocity, the flux of energy through any area is zero, the energy density is same throughout the space, the medium possesses no net energy)

61. When stationary waves are set up in a medium then __________.

(The amplitude of vibration changes simple harmonically with the distance of the particle from the origin, all particles are in the same phase, different particles of the medium have different periods of oscillation, amplitude of vibration of each particle changes simple harmonically with time)

62. When stationary waves are produced in a medium. The amplitude of vibration __________.

(of a particle changes from time to time, is the same for particles separated by half the wave length, changes simple harmonically with time, is the time for all the particles)

63. Two tuning forks A and B produce 7 beats per second, when sounded together. On loading the fork A slightly only 5 beats are heard in a second. If the frequency of fork B is 200 cps, the frequency of the fork A after loading will be __________.

(190 cps, 195 cps, 210 cps, 205 cps)

64. Two forks A and B produce 7 beats per second. On loading the fork A slightly the number of beats reduces to 5 beats per second. If the frequency of the fork B is 200cps. The frequency of the fork A before loading is __________.

(190 cps, 195 cps, 207 cps, 205 cps)

65. In stationary waves, the amplitude of vibration will have a maximum value at positions separated by a distance equal to __________.

(l, l/2, l/4, l/3)

66. In a transverse arrangement, a stretched string vibrates in two loops. If the same string under the same tension vibrates in one loop, the frequency in latter case divided by the frequency in former case will be __________.

(1, ½, 2, Ö2)

67. A source of sound wave moves away with the velocity of sound from a stationary observer. The frequency of the note is __________.

(Unchanged, Doubled, halved, squared)

68. The frequency of a man’s voice is 200 cps and its wavelength is 2 m. If the wavelength of a child’s voice is 4 m then the frequency of the child’s voice in the same medium is __________.

(200, 25, 100, 400)

69. If the densities of two gases are in the ratio 25:9 then the velocities of sound in two gases (having the same value of ratio of specific heats) at the same pressure will be in the ratio __________.

(25 : 9, 5 : 3, 9 : 25, 3 : 5)

70. The ratio of the fundamental frequency of an organ pipe open at both ends to that of the organ pipe closed at one end is __________

(1 : 2, 2 : 1, 1.5 : 1, 1 : 1)


71. The velocity of longitudinal waves passing through metal rod is proportional to the square root of __________.

(Tension, Young’s Modulus, Bulk Modulus, Rigidity)

72. The velocity of sound waves in fluid medium at absolute temperature T is directly proportional to __________.

(T, T1/2, T-1/2, T-1)

73. The velocity of transverse vibrations in sonometer under tension T is proportional to __________.

(T, T1/2, T-1/2, T-1)

74. Sound travels faster in __________.

(Air, Water, Vacuum, Glass)

75. When source of sound waves moves towards an observer at rest in the atmosphere, the pitch of the note heard by the observer is higher because __________.

(Wavelength of waves becomes smaller, Wavelength remains unchanged byt the observer receive a larger number of waves per second, The pitch of the source increases, The velocity of sound waves increases)

76. Sound waves cannot be __________.

(Reflected, Refracted, Diffracted, Polarized)

77. When a body travelling with supersonic speed approaches a stationary observer the __________.

(The pitch appears to increase, The pitch appears to decrease, The pitch is unaltered, doppler’s effect is inapplicable)

78. When sound waves travel from air to water, the quantity that remains unchanged is __________.

(Speed, Frequency, Intensity, Wavelength)

79. Velocity of sound in a gas increases with __________.

(temperature, pressure, humidity, frequency)

80. When the pressure of the gas is doubled, the velocities of sound in it are __________.

(Doubled, halved, unaltered, squared)

81. When the temperature of a gas is increased to 4 times the velocity of sound V becomes __________.

(V/4, V/2, 2V, 4V)

82. Velocity of sound is __________.

(Directly proportional to temperature, Inversely proportional to temperature, Independent of changes in pressure, Independent of amount of humidity in air)

83. Sound waves in air are __________.

(Longitudinal, Transverse, Neither longitudinal nor transverse, both longitudinal and transverse)

84. At __________ temperature will be velocity of sound be double of its value at 0°C.

(819°C, 8190°C, 81.9°C, None of these)

85. In sonometer, the frequency of a sonometer wire is given by n = 1/2L ÖT/m. Where SI unit of the symbol m is __________.

(kg, kgm-1, Nm-1, kgm-2)

86. In a vibrating tuning fork, the waves produced between the prongs of the fork are __________.

(Progressive, Simple Harmonic, Stationary, Plane)

87. The SI unit for intensity of sound is __________.

(Joule, J/s, Jm-2, Wm-2)

88. The dimensional formula for intensity is __________.

(MLT-2, MLT-3, ML°T-3, ML°T-2)

89. Stationary waves of frequency 165Hz are formed in air. If the velocity of sound waves is 330m/s, the shortest distance between two nodes is __________.

(1m, 2m, 4m, Zero)

90. Production of beats is a result of the phenomenon of __________.

(Resonance, Interference, Reflection, Diffraction)

91. As a result of interference, energy __________.

(Is lost, is gained, is transmitted, remaisn unchanged as a whole but is distributed)

92. A rope can carry a transverse wave because it has the property of __________.

(Mass, elasticity, density, compressibility)

93. The pitch of the whistle of an engine changes in the ratio of 6 : 5 as it approaches a stationary observer. If v is the velocity of sound waves, the velocity of the engine is __________.

(v, v/3, v/5, v/11)

94. The speed of wave in a rope can be increased by __________.

(Shaking the end faster, shakeing the end over a under range, stretching the rope tighter, using a heavier rope)

95. Doppler’s effect applies to __________.

(Onkly sound waves, only light waves, both sound and light waves, neither sound nor light waves)

96. The distance from crest to crest of any wave is called its __________.

(Frequency, Wavelength, Speed, Amplitude)

97. Sound travels fastest in __________.

(Air, Water, Iron, Vacuum)

98. When source and observer are moving away from each other the apparent pitch will __________.

(Increase, Decrease, Remain same, Become infinite)

99. __________ of the following is the SI unit of frequency.

(Hertz, cycles/sec, netwon, erg)

100. For a closed pipe, the second overtone is the __________.

(Second harmonic, Third harmonic, Fourth harmonic, Fifth harmonic)

101. A wave in which the particles of the material move up and down as the wave goes from left to right is classed as __________.

(Longitudinal, Transverse, Compressional, Sound)

102. As a man move directly away from a steady source of sound at constant speed, the sound he hears will __________.

(Increase in frequency and intensity, decrease in frequency and intensity, stay constant in pitch but decrease in loudness, remain constant in both pitch and loudness)

103. Decibel is __________.

(A musical instrument, musical note, a measure of intensity level, the wavelength of noise)

104. Increased loudness produced when two bodies vibrate sympathetically is called __________.

(An echo, beats, destructive interference, resonance)

105. Damping is a __________.

(Reduction in frequency, Reduction in wavelength, reduction in amplitude, All of these)

106. Wavelength is the distance between two nearest particles of the medium having phase difference __________.

(p/4, p/2, p, 0)

107. At the mean position of vibration, the velocity of the vibrating particle is __________.

(Zero, Infinity, Maximum, None of these)

108. The pitch of a sound is determined by its __________.

(Speed, Frequency, Direction, Number of beats)

109. When the soldiers corss a bridge, they are advised to march out of step due to the __________.

(Resonance, High frequency, Noise produced, Fact thath bridge is weak)

110. A pulse on a string is inverted when it is reflected from a __________.

(free end, fixed end, both free and fixed end, none of these)

111. When two vibrating systems are in resonance, then their __________.

(Amplitude are equal, Frequencies are equal, Resistances are equal, Temperatures are equal)

112. Sounds above a frequency of 20000 Hz are called __________.

(Supersonic, infrasonic, hypersonic, ultrasonic)

113. When waves go from one place to another, they transport __________.

(Amplitude, Frequency, Wavelength, Energy)

114. Transverse waves are traveling along string, when the tension is increased to four times its original value, the velocity of the waves is __________.

(Doubled, reduced to one half, reduced to one fourth, increased to four times its original value)

115. To produce beats it is necessary to used two waves __________.

(traveling in opposite direction, of slightly different frequencies, of equal wavelength, of equal amplitude)

116. The amplitude of sound wave determines its __________.

(Loudness, Pitch, Reverberation, Interference)

117. Overtones are __________.

(Beats, the fundamental produced in a pipe, the notes produced in a pipe other than the fundamental, all of these)

118. Two tuning forks of 340 and 343 Hz are sounded together. The resulting beats per second will be __________.

(1, 2, 3, 4)

119. The speed of sound waves in air having a frequency of 256 Hz compared with the speed of sound waves having a frequency of 512 Hz is __________.

(half as great, the same, twice as great, four times as great)

120. The apparent change in frequency due to a relative motion between the source and the observer is known as __________.

(Laplace’s Priciple, Sabine’s Principle, Newtonian’s Principle, Doppler’s Principle)

121. If E is the coefficient of volume elasticity (Bulk Modulus) of the medium and d its density, then the velocity of a longitudinal wave in fluid is given by __________.

(v = E/P, v = ÖE/d, v = P/E, v = ÖP/E)

122. We know that the velocity of sound obtained from Newton’s formula is much less than the experimental value. The reason for this is __________.

(Sound travels in air under isothermal conditions, soundtravels in air under adiabatic conditions, sound travels in air as a transverse wave motion, none of these is correct)

123. Velocity of sound as given by Laplace is __________.

(v = Ögr/d, v = rÖg/d, v = gr/d, v = gÖr/d)

124. It is possible to recognize a person by hearing his voice even if he is hidden behind a solid wall. This is due to the fact that his voice __________.

(has a definite pitch, has a definite quality, has a definite capacitor, can penetrate the wall)

125. Two waves arrive simultaneously at a point in phase. The disturbance, at the point, due to each wave is 2.5 mm and 3.5 mm respectively the resultant disturbance is __________.

(2.5 mm, 6 mm, 3.5 mm, 1mm)

126. Successive nodes or antinodes occur at points, separation between which is __________.

(l/4, l/2, 3l/4, l)

127. The period of pendulum is determined by its __________.

(Length, Mass, Maximum Speed, Amplitude)

128. Red shift indicates the __________.

(Aproach of a star, Recession of a star, Stationary State of a Star, Size of a star)