WBCHSE Class 11 Physics Wave Motion Multiple Choice Questions

Wave Motion Multiple Choice Questions And Answers

Question 1. Which one of the following phenomena differentiates transverse waves from longitudinal waves?

1. Reflection
2. Refraction
3. Polarisation
4. Interference

Answer: 3. Polarisation

Question 2. A sound wave is a

1. Transverse elastic wave
2. Transverse electromagnetic wave
3. Longitudinal elastic wave
4. Longitudinal electromagnetic wave

Answer: 3. Longitudinal elastic wave

Question 3. A light wave is a

1. Transverse elastic wave
2. Transverse electromagnetic wave
3. Longitudinal elastic wave
4. Longitudinal electromagnetic wave

Answer: 2. Transverse electromagnetic wave

Question 4. Polarisation of the sound wave does not occur, because the sound wave is

1. Transverse wave
2. Longitudinal wave
3. Progressive wave
4. Elastic wave

Answer: 2. Longitudinal wave

Question 5. If a child stands up while swinging on a swing, then the period of the swing will

1. Increase
2. Decrease
3. Remain same
4. Increase if the child is long and decrease if the child is short

Answer: 2. Decrease

Question 6. A wave is advancing along the surface of water with a velocity of 80 cm · s^-1. If the distance between two consecutive crests is 20 cm, then what will be the wavelength?

1. 80 cm
2. 20 cm
3. 4 cm
4. \(\frac{1}{4}\) cm

Answer: 2. 20 cm

Question 7. When a wave coming from a medium enters another medium, the property of the wave which remains unchanged is

1. Velocity
2. Frequency
3. Wavelength
4. Amplitude

Answer: 2. Frequency

Question 8. A wave is advancing along the surface of water with a velocity of 80 cm • s^-1. If the distance between two consecutive crests is 20 cm, then what will be the frequency of the wave?

1. 80Hz
2. 20Hz
3. 4 Hz
4. \(\frac{1}{4}\) Hz

Answer: 3. 4 Hz

Question 9. When a force F₁ acts on a particle, the frequency is 6Hz, and when a force F₂ acts, the frequency is 8 Hz. Now if both the forces act simultaneously in the same direction, then their frequency’ becomes

1. 20Hz
2. 14Hz
3. 10Hz
4. 2Hz

Answer: 3. 10Hz

Question 10. If the wavelength in a medium is reduced by 50%, keeping its velocity constant, the percentage change in its frequency is

1. 50%
2. 25%
3. 100%
4. 200%

Answer: 3. 100%

Question 11. The equation of a progressive wave is given by y = \(5 \sin \frac{\pi}{2}(100 t-x) \mathrm{cm}\). The wavelength is

1. 2 cm
2. 4 cm
3. 50 cm
4. 100 cm

Answer: 2. 4 cm

Question 12. The equation of a progressive wave is given by y = \(5 \sin \frac{\pi}{2}(100 t-x) \mathrm{cm}\). The frequency of the wave is

1. 25 Hz
2. 50 Hz
3. 100 Hz
4. 50π Hz

Answer: 1. 25 Hz

Question 13. The equation of a wave is given by y = \(10^{-4} \sin (60 t+2 x)\). Here x is expressed in metres and r in seconds. This represents a wave

1. Which is moving in the negative direction of the x-axis with a velocity of 30 m • s^-1
2. Whose wavelength is  πm
3. Whose frequency’ is \(\frac{30}{\pi}\) hz
4. All the above options are correct

Answer: 4. All the above options are correct

Question 14. The equation of a tramverse wave is given by Y = \(Y_0 \sin 2 \pi\left(f t-\frac{x}{\lambda}\right)\). If the wave velocity, then

1. \(\lambda=\frac{\pi Y_0}{4}\)
2. \(\lambda=\frac{\pi Y_0}{2}\)
3. \(\lambda=\pi Y_0\)
4. \(\lambda=2 \pi Y_0\)

Answer: 2. \(\lambda=\frac{\pi Y_0}{2}\)

Question 15. Which one of the following physical quantities moves with a wave at the same velocity?

1. Amplitude
2. Mass
3. Momentum
4. Energy

Answer: 4. Energy

Question 16. When temperature increases, the frequency of a turning fork,

1. Increases
2. Decreases
3. Remains same
4. Increases or decreases depending on the material

Answer: 2. Decreases

Question 17. The pressure, density, and ratio of two specific heats of a gas are p, ρ, and γ respectively. The velocity of sound in the gas is

1. \(\frac{\sqrt{p}}{\rho}\)
2. \(\gamma \frac{\sqrt{p}}{\rho}\)
3. \(\sqrt{\frac{\gamma p}{\rho}}\)
4. \(\sqrt{\frac{3 \gamma p}{\rho}}\)

Answer: 3. \(\sqrt{\frac{\gamma p}{\rho}}\)

Question 18. If the absolute temperature of a gas is T and the velocity’ of sound in the gas is V, then

1. V ∝ T
2. V ∝ √T
3. \(V \propto \frac{1}{T}\)
4. \(V \propto \frac{1}{\sqrt{T}}\)

Answer: 2. V ∝ √T

Question 19. The velocity of sound in moist air is greater than that in dry air, because

1. Moist air is comparatively light
2. Moist air is comparatively heavy
3. The pressure of moist air is low
4. The pressure of moist air is high

Answer: 1. Moist air is comparatively light

Question 20. Laplace concluded that the temperature of a gaseous medium cannot remain constant during the propagation of sound through it, because

1. The pressure of the gas remains constant
2. The volume of the gas remains constant
3. The particles of the medium vibrate with a large amplitude
4. The compressions and the rarefactions occur very rapidly

Answer: 4. The compressions and the rarefactions occur very rapidly

Question 21. According to Laplace’s correction, the propagation of sound through a gaseous medium is

1. An isochoric process
2. An isobaric process
3. An isothermal process
4. An adiabatic process

Answer: 4. An isochoric process

Question 22. In an adiabatic process, the bulk modulus of a gas is

1. Equal to its density
2. Greater than its density
3. Equal to its pressure
4. Greater than its pressure

Answer: 4. Greater than its pressure

Question 23. The velocity of sound in air at STP is 330 m· s^-1. If the atmospheric pressure becomes 75 cm Hg, then the velocity of sound at the same temperature will be

1. 330 m · s^-1
2. Less than 330 m · s^-1
3. Greater than 330 m · s^-1
4. Given data is insufficient

Answer: 1. 330 m · s^-1

Question 24. For 1°C rise in temperature, the velocity of sound in air increases by

1. About 2 m · s^-1
2. About 2 ft · s^-1
3. About 61 m · s^-1
4. About 61 ft · s^-1

Answer: 2. About 2 ft · s^-1

Question 25. The ratio of the velocities of sound through hydrogen and oxygen at STP is

1. 1:16
2. 1:4
3. 4:1
4. 16:1

Answer: 3. 4:1

Question 26. At what temperature the velocity of sound in a gas will increase by 10% of its value at 27 °C?

1. 29.7°C
2. 32.7°C
3. 57°C
4. 90°C

Answer: 4. 90°C

Question 27. TWo monatomic ideal gases of molecular masses m₁ and m₂ respectively are enclosed in separate containers and kept at the same temperature. The ratio of the speed of sound of 1st and 2nd gas is given by

1. \(\sqrt{\frac{m_1}{m_2}}\)
2. \(\sqrt{\frac{m_2}{m_1}}\)
3. \(\frac{m_1}{m_2}\)
4. \(\frac{m_2}{m_1}\)

Answer: 2. \(\sqrt{\frac{m_2}{m_1}}\)

Question 28. Velocity of sound is maximum in

1. Water
2. Air
3. Vacuum
4. Steel

Answer: 4. Steel

Question 29. The ratio of the speed of sound in nitrogen gas to that in helium gas, at 300K is

1. \(\sqrt{\frac{2}{7}}\)
2. \(\sqrt{\frac{1}{7}}\)
3. \(\frac{\sqrt{3}}{5}\)
4. \(\frac{\sqrt{6}}{5}\)

Answer: 3. \(\frac{\sqrt{3}}{5}\)

Question 30. During a speech, the vibration of the diaphragm of a microphone is

1. Natural vibration
2. Damped vibration
3. Forced vibration
4. Resonant vibration

Answer: 3. Forced vibration

Question 31. Phon is the unit of

1. Pitch
2. Quality
3. Timbre
4. Loudness

Answer: 4. Loudness

Question 32. A sound absorber attenuates the sound level by 20 dB. The intensity decreases by a factor of

1. 1000
2. 10000
3. 10
4. 100

Answer: 4. 100

Question 33. Which one of the following phenomena does not take place in the case of sound waves?

1. Reflection
2. Refraction
3. Polarisation
4. Interference

Answer: 3. Polarisation

Question 34. A balloon full of carbon dioxide and another full of water behaves as lenses for the refraction of sound. What will be the nature of these lenses?

1. Both are convergent
2. Both are divergent
3. The first one is divergent and the second one is convergent
4. The first one is convergent and the second one is divergent

Answer: 4. The first one is convergent and the second one is divergent

Question 35. If a man standing at any place between two hills fires a gun, how many echoes will he hear?

1. 1
2. 2
3. 4
4. More than 4

Answer: 4. More than 4

Question 36. A sound is made in sea water from the bottom of a ship and its echo is heard after a time t. If v is the velocity of sound in sea water, the depth of the sea at that place is

1. vt
2. \(\frac{v t}{2}\)
3. \(\frac{v t}{10}\)
4. \(\frac{v t}{20}\)

Answer: 2. \(\frac{v t}{2}\)

Question 37. An echo coming from a hill is heard 20 s after the original sound. If the velocity of sound in air is 330 m • s^-1, the distance of the hill will be

1. 3.3 km
2. 6.6 km
3. 1.65 km
4. 13.2 km

Answer: 1. 3.3 km

Question 38. If the velocity of sound in air and in water are 330 m · s^-1 and 1400 m · s^-1 respectively, what will be the critical angle for refraction of sound going to water from air?

1. About 29°
2. About 13.6°
3. About 76.4°
4. No critical angle in this case

Answer: 2. About 13.6°

Question 39. A source of sound of frequency 600 Hz is placed in water. The speed of sound in water and air is 1500 m/s and 300 m/s respectively. The frequency of sound recorded by an observer who is standing in air is

1. 660 Hz
2. 600 Hz
3. 540 Hz
4. None of the above

Answer: 2. 600 Hz

In this type of question, more than one option is correct.

Question 40. A wave equation that gives the displacement along the y-direction is given by y = 10^-4 sin(60t+2x) where x and y are in meters and t is time in seconds. This represents a wave

1. Traveling with a velocity of 30 m · s^-1 in the negative x -direction
2. Of wavelength πm
3. Of frequency \(\frac{30}{\pi}\) hz
4. Of amplitude 10^-4 m traveling along the negative x -direction

Answer: All options are correct

Question 41. For a transverse wave on a string, the string displacement is described by, y = f(x- at) where f represents a function and A is a negative constant. Then which of the following is/are correct statement(s)?

1. The shape of the string at time t = 0 is given by f(x)
2. The shape of the waveform doesn’t change as it moves along the string.
3. Waveform moves in the positive x -x-direction
4. The speed of the waveform is a.

Answer:

1. The shape of the string at time t = 0 is given by f(x)
2. The shape of the waveform doesn’t change as it moves along the string.

Question 42. Mark the correct statement(s) concerning waves

1. A wave can have both transverse and longitudinal components
2. A wave doesn’t result in the bulk flow of the materials of its medium
3. A wave is a traveling disturbance
4. A wave can be there even in the absence of an elastic medium

Answer: All options are correct

Question 43. Mark the correct statements.

1. Note emitted from any musical instrument is generally a combination of tones
2. A tone can be compared with compound light
3. Fundamental tone can be treated as the 1st harmonic
4. Harmonics are only the odd multiples of the fundamental tone

Answer:

1. Note emitted from any musical instrument is generally a combination of tones

3. Fundamental tone can be treated as the 1st harmonic

Question 44. Suppose a musical instrument emits sound having frequencies 250 Hz, 300 Hz, 350 Hz, 400 Hz, 450 Hz, and 500 Hz respectively.

1. Tones having frequencies 250 Hz, 300 Hz, 350 Hz, 400 Hz, 450 Hz, and 500 Hz are overtones.
2. The tone of 250 Hz is the fundamental tone
3. The combination of these six tones forms a note
4. The tone of 500 Hz is the octave

Answer:

2. The tone of 250 Hz is the fundamental tone

3. Combination of these six tones forms a note

4. The tone of 500 Hz is the octave