Physics · Science General

Acoustics and Sound Waves

2,160 Questions

Acoustics and sound waves deal with mechanical vibrations traveling through media like air and water. Key concepts include wave reflection, beats, echoes, the Mach number, and infrasound. These physics fundamentals are regularly tested in general science sections of multiple competitive exams.

Sound wave propagationEchoes and reflectionWave interferenceMach numberInfrasound frequency

Acoustics and Sound Waves Questions

Multiple choice

Doppler's effect is associated with ________.

  1. sound

  2. light

  3. magnetism

  4. electromagnetic induction
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

Doppler effect describes the change in frequency/wavelength of a wave when the source and observer are in relative motion. While commonly taught with sound examples (siren pitch changing as ambulance passes), it applies to all waves including light (redshift/blueshift).

Multiple choice

The speed of sound in air is ______.

  1. 340 m per second

  2. 2 x 108 m per second

  3. 20 m per second

  4. none of these
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

At standard temperature (20°C) and pressure, sound travels through air at approximately 340-343 meters per second. This value varies with temperature (speed increases with temperature) but 340 m/s is the standard approximation used in textbooks and calculations.

Multiple choice

One cannot hear sound on the moon because it has no _____.

  1. atmosphere

  2. light

  3. darkness

  4. gravity
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

Sound is a mechanical wave that requires a material medium (solid, liquid, or gas) to propagate. The moon has essentially no atmosphere - only an extremely thin exosphere - so there are insufficient air molecules to transmit sound waves from one point to another.

Multiple choice

What does loudness of sound depend upon?

  1. Its pitch

  2. Its frequency

  3. Its amplitude

  4. Its range
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

Loudness is a perceptual quantity directly related to the amplitude of sound waves. Larger amplitude means greater displacement of air molecules, more energy, and perception of louder sound. Pitch depends on frequency, not loudness.

Multiple choice

In which of the following mediums sound travels at maximum speed?

  1. Air

  2. Vacuum

  3. Steel

  4. Water
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

Sound travels fastest in solids (steel: ~5000-6000 m/s) because molecules are tightly packed and interactions are rapid. Speed is slower in liquids (water: ~1500 m/s) and slowest in gases (air: ~340 m/s) due to increasing molecular distances. Sound cannot travel in vacuum as there is no medium.

Multiple choice

The reverberation of sound in a hall is due to continued ______.

  1. reflection

  2. interference

  3. defraction

  4. absorption
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

Reverberation is the persistence of sound in an enclosed space due to multiple reflections from walls, ceiling, and other surfaces. When sound waves continue to reflect off surfaces rather than being absorbed, they create the prolongation of sound known as reverberation.

Multiple choice

What is the unit for measuring the pitch of frequency of sound?

  1. Coulomb

  2. Hertz

  3. Decibel

  4. Cycles
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

Hertz (Hz) is the SI unit for frequency, measuring cycles per second. While pitch is a perceptual quality of sound, the physical frequency that determines pitch is measured in Hz. Decibel measures intensity level, coulomb measures electric charge, and 'cycles' is not a standard unit.

Multiple choice

Fathom is the unit of

  1. sound

  2. depth

  3. distances

  4. frequency
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

A fathom is a unit of depth equal to 6 feet (approximately 1.83 meters), traditionally used for measuring water depth in navigation and maritime contexts. It is not used for measuring sound, general distances, or frequency.

Multiple choice

Which of the following statements is/are false? a. Sound is produced when an object moves to and fro rapidly. b. The energy required to make an object vibrate and produce sound is produced by some outside source. c. Sound of a radio speaker is produced due to the vibrating air columns of the speaker.

  1. Only a

  2. Only a and b

  3. Only b

  4. Only b and c

  5. Only c
Reveal answer Fill a bubble to check yourself
E Correct answer
Explanation

This is the correct option, as this statement is false. Sound of a radio speaker is not produced due to the vibrating air columns of the speaker. It is due to the vibrations of the cone of speaker.

Multiple choice

Due to which of the following reasons, sound cannot be heard on the surface of moon?

a. Due to absence of gravity. b. Due to absence of air on moon. c. Due to uneven terrain on moon.

  1. Only a and b

  2. Only a

  3. Only b and c

  4. Only b

  5. Only c
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

This is the correct option. Sound waves need a medium to travel. As there is no air on moon, there is no medium for air waves to travel. Thus, sound cannot be heard on the surface of moon.