## Wave Motion Multiple Choice Questions And Answers

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

- Reflection
- Refraction
- Polarisation
- Interference

**Answer:** 3. Polarisation

**Question 2. A sound wave is a**

- Transverse elastic wave
- Transverse electromagnetic wave
- Longitudinal elastic wave
- Longitudinal electromagnetic wave

**Answer:** 3. Longitudinal elastic wave

**Question 3. A light wave is a**

- Transverse elastic wave
- Transverse electromagnetic wave
- Longitudinal elastic wave
- Longitudinal electromagnetic wave

**Answer:** 2. Transverse electromagnetic wave

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

- Transverse wave
- Longitudinal wave
- Progressive wave
- 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**

- Increase
- Decrease
- Remain same
- 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?**

- 80 cm
- 20 cm
- 4 cm
- \(\frac{1}{4}\) 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**

- Velocity
- Frequency
- Wavelength
- 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?**

- 80Hz
- 20Hz
- 4 Hz
- \(\frac{1}{4}\) Hz

**Answer:** 3. 4 Hz

**Question 9. When a force F _{1} acts on a particle, the frequency is 6Hz, and when a force F_{2} acts, the frequency is 8 Hz. Now if both the forces act simultaneously in the same direction, then their frequency’ becomes**

- 20Hz
- 14Hz
- 10Hz
- 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**

- 50%
- 25%
- 100%
- 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**

- 2 cm
- 4 cm
- 50 cm
- 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**

- 25 Hz
- 50 Hz
- 100 Hz
- 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**

- Which is moving in the negative direction of the x-axis with a velocity of 30 m • s
^{-1} - Whose wavelength is πm
- Whose frequency’ is \(\frac{30}{\pi}\) hz
- 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**

- \(\lambda=\frac{\pi Y_0}{4}\)
- \(\lambda=\frac{\pi Y_0}{2}\)
- \(\lambda=\pi Y_0\)
- \(\lambda=2 \pi Y_0\)

**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?**

- Amplitude
- Mass
- Momentum
- Energy

**Answer:** 4. Energy

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

- Increases
- Decreases
- Remains same
- 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**

- \(\frac{\sqrt{p}}{\rho}\)
- \(\gamma \frac{\sqrt{p}}{\rho}\)
- \(\sqrt{\frac{\gamma p}{\rho}}\)
- \(\sqrt{\frac{3 \gamma p}{\rho}}\)

**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**

- V ∝ T
- V ∝ √T
- \(V \propto \frac{1}{T}\)
- \(V \propto \frac{1}{\sqrt{T}}\)

**Answer:** 2. V ∝ √T

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

- Moist air is comparatively light
- Moist air is comparatively heavy
- The pressure of moist air is low
- 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**

- The pressure of the gas remains constant
- The volume of the gas remains constant
- The particles of the medium vibrate with a large amplitude
- 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**

- An isochoric process
- An isobaric process
- An isothermal process
- An adiabatic process

**Answer:** 4. An isochoric process

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

- Equal to its density
- Greater than its density
- Equal to its pressure
- 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**

- 330 m · s
^{-1} - Less than 330 m · s
^{-1} - Greater than 330 m · s
^{-1} - 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**

- About 2 m · s
^{-1} - About 2 ft · s
^{-1} - About 61 m · s
^{-1} - 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**

- 1:16
- 1:4
- 4:1
- 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?**

- 29.7°C
- 32.7°C
- 57°C
- 90°C

**Answer:** 4. 90°C

**Question 27. TWo monatomic ideal gases of molecular masses m _{1} and m_{2} 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**

- \(\sqrt{\frac{m_1}{m_2}}\)
- \(\sqrt{\frac{m_2}{m_1}}\)
- \(\frac{m_1}{m_2}\)
- \(\frac{m_2}{m_1}\)

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

**Question 28. Velocity of sound is maximum in**

- Water
- Air
- Vacuum
- Steel

**Answer:** 4. Steel

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

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

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

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

- Natural vibration
- Damped vibration
- Forced vibration
- Resonant vibration

**Answer**: 3. Forced vibration

**Question 31. Phon is the unit of**

- Pitch
- Quality
- Timbre
- Loudness

**Answer:** 4. Loudness

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

- 1000
- 10000
- 10
- 100

**Answer:** 4. 100

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

- Reflection
- Refraction
- Polarisation
- 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?**

- Both are convergent
- Both are divergent
- The first one is divergent and the second one is convergent
- 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
- 2
- 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**

- vt
- \(\frac{v t}{2}\)
- \(\frac{v t}{10}\)
- \(\frac{v t}{20}\)

**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**

- 3.3 km
- 6.6 km
- 1.65 km
- 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?**

- About 29°
- About 13.6°
- About 76.4°
- 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**

- 660 Hz
- 600 Hz
- 540 Hz
- 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**

- Traveling with a velocity of 30 m · s
^{-1}in the negative x -direction - Of wavelength πm
- Of frequency \(\frac{30}{\pi}\) hz
- 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)?**

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

**Answer:**

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

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

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

**Answer:** All options are correct

**Question 43. Mark the correct statements.**

- Note emitted from any musical instrument is generally a combination of tones
- A tone can be compared with compound light
- Fundamental tone can be treated as the 1st harmonic
- 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.**

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