Physics ยท Science General

Acoustics and Sound Waves

2,006 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

Sound travels faster in

  1. dry air than in water

  2. wood than in iron

  3. iron than in air

  4. hydrogen than in water
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

Sound travels fastest in solids because molecules are tightly packed, allowing vibrations to propagate quickly. The speed of sound is approximately 5130 m/s in iron (solid), 1482 m/s in water (liquid), 343 m/s in air (gas), and about 1270 m/s in hydrogen. The denser and more elastic the medium, the faster sound travels through it.

Multiple choice

In amplitude modulation,

  1. both amplitude and frequency change unequally

  2. both amplitude and frequency change equally

  3. only amplitude is changed and frequency remains constant

  4. only frequency changes
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

In amplitude modulation, only amplitude of the carrier waves is changed and the frequency remains constant.

Multiple choice

Threshold stimulus is ______ than the resting potential.

  1. slow

  2. less

  3. more

  4. None of the above
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

The threshold stimulus must be more positive (less negative) than the resting membrane potential. Typically, the resting potential is around -70 mV, and threshold is around -55 mV, meaning the membrane must depolarize by about 15 mV to reach threshold and trigger an action potential.

Multiple choice

The maximum limit of sound beyond which a person can become deaf is

  1. 55 db

  2. 75 db

  3. 85 db

  4. 120 db
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

Prolonged exposure to sounds at or above 120 dB can cause permanent hearing damage and deafness. This level of intensity is comparable to a jet engine at close range. Sounds at 85 dB can cause damage with long-term exposure, but 120 dB is the threshold where immediate damage becomes significant.

Multiple choice

Speed of sound in air is unaffected by change in

  1. pressure

  2. humidity

  3. temperature

  4. volume
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

The speed of sound in an ideal gas depends on temperature and gas composition, but is independent of pressure at constant temperature. Humidity affects it (water vapor changes gas properties), temperature affects it directly, and 'volume' is not a property that changes the speed of sound in the physics context of this question.

Multiple choice

Speed of sound is maximum in

  1. water

  2. vacuum

  3. air

  4. steel
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

Sound travels fastest in solids because molecules are tightly packed, allowing efficient energy transfer. Steel's density and elasticity make sound travel at ~5000 m/s, much faster than in air (~340 m/s). Sound cannot travel in vacuum.

Multiple choice

Sound waves cannot travel through

  1. vacuum

  2. liquids

  3. solids

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

Sound waves are mechanical waves that require a physical medium (solid, liquid, or gas) to propagate. The particles in the medium vibrate and transfer energy through collisions. A vacuum is the absence of matter, so there are no particles to vibrate and transmit the sound wave. This is why sound cannot travel through space.

Multiple choice

Sound is produced by

  1. heating

  2. cooling

  3. a rotating body

  4. a vibrating body

  5. a moving body
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

Sound is produced by a vibrating body.

Multiple choice

Audio refers to

  1. seeing with the eyes

  2. smelling with the nose

  3. hearing with the ears

  4. feeling with the skin
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

The term 'audio' comes from the Latin word 'audire', which means 'to hear'. It refers to anything related to sound or the sense of hearing.