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 resonance oscillations physics

Some opera singers are able to use their voice to shatter a crystal glass. Which of the phenomenon is used to explain this ? 

  1. Acoustic reflection

  2. Multiple echoes

  3. Interference

  4. Resonance

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

 When the  external frequency becomes equal to the natural frequency of the body , then the amplitude of vibrations of the body becomes very large , this phenomenon is called resonance .

   When a opera singer  manages his frequency such that it becomes equal to the natural frequency of crystal glass , resonance occurs and glass shatters.

Multiple choice resonance oscillations physics

Your friend is playing a song on a piano. Whenever your friend hits a certain key, the lamp on top of the piano rattles. Explain why the lamp rattles.

  1. The lamp rattles because of the occurring of interference

  2. The lamp rattles because of the occurring of diffraction

  3. The lamp rattles because of the occurring of resonance

  4. None of the above

Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

This happens due to resonance (A phenomenon in which a vibrating system or external force drives another system to oscillate with a greater amplitude at a specific frequency). The lamp on top of the piano has a resonant frequency equal to one of the notes being played.

Multiple choice resonance oscillations physics

During resonance, sound waves tend to absorb

  1. more energy

  2. less energy

  3. no energy

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

System to absorb more energy when the frequency of its oscillations matches the system's natural frequency of vibration than it does at other frequencies.

Multiple choice resonance oscillations physics

A glass tube of $1.0 m$ length is filled with water. The water can be drained out slowly at bottom of the tube. If a vibrating turning fork of frequency $500 Hz$ is brought at the upper end of the tube and the velocity of sound is $330 \,\,m\,\,s^{-1}$, then the total number of resonances obtained will be:

  1. 4

  2. 3

  3. 2

  4. 1
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

Wavelength of the sound produced is,
$\lambda = \dfrac{Velocity}{Frequency} $


$= \dfrac{330\,\,m\,\,s^{-1}}{500\,\,s^{-1}} = 0.66\,\,m$
The resonance occurs at
$\dfrac{\lambda}{4},\dfrac{3\lambda}{4},\dfrac{5\lambda}{4},\dfrac{7\lambda}{4},.....$
i.e., at $0.165\,\,m, 0.495\,\,m, 0.825\,\,m, 1.155\,\,m$. As the length of the tube is only $1.0\,\,m$, hence $3$ resonance will be observed.

Multiple choice biology physical resources air and winds wind energy air as a natural resource

What scale is useful to record the force of wind ?

  1. Decibel

  2. Richter

  3. Beau fort

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

The Beaufort scale is an empirical measure that relates wind speed to observed conditions at sea or on land. It ranges from 0 (calm) to 12 (hurricane-force winds). Decibels measure sound intensity, Richter scale measures earthquake magnitude, and Fujita scale (misspelled as Fajita here) measures tornado intensity.

Multiple choice physics study of sound determination of speed of sound by echo problems on sound sound needs a medium

A sound wave travels from west to east, in which direction do the particles of air move?

  1. west-east

  2. south-north

  3. up-down

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

Sound waves are longitudinal waves and the particles of the air move in direction of propagation sound. So if the wave will travel in west-east direction,the particles of the air also travels in west-east direction.

Multiple choice physics study of sound determination of speed of sound by echo problems on sound sound needs a medium

Mark the incorrect statement

  1. Sound can be produced by beating an object irrespective of whether there are vibrations or not.

  2. The sound of a tabla normally has a lower pitch than the sound of a violin.

  3. A short flute will produce sound of lower pitch than a long flute.

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

(i) False [Sound is produced from a vibrating object.]

(ii) True [The sound of a tabla normally has a lower pitch than the sound of a violin.]

(iii) True[A short flute will produce sound of lower pitch than a long flute.]

Multiple choice physics study of sound determination of speed of sound by echo problems on sound sound needs a medium

Why are the regions of compressions and rare fractions of sound waves formed?

  1. A sound wave undergoes diffraction behind obstacles.

  2. The reflected sound wave at a fixed end interferes with the incident wave.

  3. The longitudinal movement of air molecules produces pressure fluctuations.

  4. The speed of the sound wave changes as its travels through a medium.
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

Longitudinal waves are made up of compressions and rarefactions. Compression happens when molecules are forced, or pressed, together. Rarefaction is just the opposite, it occurs when molecules are given extra space and allowed to expand. So, the longitudinal movement of air molecules produces pressure fluctuations which results in compression and rarefaction.

Multiple choice physics study of sound determination of speed of sound by echo problems on sound sound needs a medium

A source emits the sound of frequency $600\ Hz$ inside water. The frequency heard in air will be equal to (velocity of sound in watere$=1500\ m/s$, velocity of sound in air$=300\ m/s$)

  1. $3000\ Hz$
  2. $120\ Hz$
  3. $600\ Hz$
  4. $6000\ Hz$
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

Frequency heard in the air will also be $600\space Hz.$ Whenever, the wave travels from one medium to another medium, its speed and wavelength changes but frequency remains same.

Multiple choice physics study of sound determination of speed of sound by echo problems on sound sound needs a medium

The phenomenon of sound propagation in air is 

  1. Isothermal process

  2. Isobaric process

  3. Adiabatic process

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

the point that there is a local change in temperature due to the compression and rarefaction half$-$ cycles of the waveform and that the these changes occur so quickly that no heat can enter or leave the cycle$,$

So$,$ it callesan adiabatic process$.$
Hence,
option $(C)$ is correct answer.

Multiple choice physics study of sound determination of speed of sound by echo problems on sound sound needs a medium

A sound wave travels from south to north, in which direction do the particles of air move?

  1. west-east

  2. south-north

  3. Up-down

  4. None of these
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

Sound waves are longitudinal waves and the particles of the air move in direction of propagation sound. So if the wave will travel in south-north direction,the particles of the air also travels in south-north direction.

Multiple choice physics study of sound determination of speed of sound by echo problems on sound sound needs a medium

Sound travels in air if

  1. particles of medium travel from one place to another

  2. there is no moisture in the atmosphere

  3. disturbance moves

  4. both particles as well as disturbance travel from one place to another.
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

A wave is a disturbance caused in a medium. In the case of sound, only the disturbances moves causing the surround air molecules to vibrate to and fro. The disturbance is transmitted in the form of compressions and rarefactions.