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 physics world of sounds characteristics of sound wave time period, frequency and amplitude of sound sound waves are longitudinal waves

Mark the correct statement

  1. Hard surfaces are good reflectors of sound

  2. Soft surfaces are poor reflectors of sound

  3. Bad reflectors of sound are good absorbers of sound

  4. All the above are true
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

Sound is not reflected equally from different materials. Hard surfaces reflect more sound. Hard surfaces are good reflectors of sound. 
Soft or porous surfaces are poor reflectors of sound. Bad reflectors of sound are good absorbers of sound. These sound absorbing materials are used to cover walls, ceilings etc.

Multiple choice physics world of sounds characteristics of sound wave time period, frequency and amplitude of sound sound waves are longitudinal waves

Explain why, if we strike a table lightly, we hear a soft sound but if we hit the table hard, a loud sound is heard.

  1. When a table is striked lightly,vibrations are produced with less amplitude

  2. When the table is strikes hard,the amplitude is high

  3. Both

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

If we strike a table lightly the vibrations produced have less amplitude than when we strike the table hard. Since loudness depends on amplitude, soft sound is heard when we strike lightly.

Multiple choice physics world of sounds characteristics of sound wave time period, frequency and amplitude of sound sound waves are longitudinal waves

Which of the following is not a characteristics of mechanical waves? 

  1. They consist of disturbances or oscillations of a medium

  2. They transport energy.

  3. They travel in a direction that is at right angles to the direction of the particles of the medium.

  4. They are created by vibrating source.

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

All of the above are the characteristics except mechanical waves travel in a direction that is at right angles to the direction of the particles of the medium. 

Multiple choice physics world of sounds characteristics of sound wave time period, frequency and amplitude of sound sound waves are longitudinal waves

Find out the relationship between the frequency and amplitude of a sound wave?

  1. Frequency is proportional to amplitude

  2. Frequency is proportional to the square of the amplitude

  3. Frequency is inversely proportional to amplitude

  4. Frequency is inversely proportional to the square of the amplitude

  5. Frequency and amplitude are independent
Reveal answer Fill a bubble to check yourself
E Correct answer
Explanation

Frequency of a wave is $f=1/T$ where T be the time period of the wave.

As time period does not depend on the amplitude so frequency is also independent of amplitude.  

Multiple choice physics world of sounds characteristics of sound wave time period, frequency and amplitude of sound sound waves are longitudinal waves

Compressional wave among the following is?

  1. X-ray

  2. Cosmic ray

  3. Radio wave

  4. Light wave

  5. Sound wave
Reveal answer Fill a bubble to check yourself
E Correct answer
Explanation

X-ray, cosmic ray, radio wave, light wave, they all  are electromagnetic waves and we know that an electromagnetic wave is always  a transverse wave, on the other hand sound wave is a mechanical longitudinal wave which propagates in a medium with compressions and rarefactions. Therefore, sound wave is a compressional wave among them.

Multiple choice physics world of sounds characteristics of sound wave time period, frequency and amplitude of sound sound waves are longitudinal waves

Sound waves do not exhibit polarization because, unlike light waves, they are not:

  1. longitudinal

  2. coherent

  3. dispersive

  4. transverse

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

In polarization the vibrations of electric vector of light are restricted by a polariser in a single plane  because vibrations are perpendicular to the propagation of light ,  as light is a transverse wave .
Polarization is the phenomenon of transverse waves only , it does not happen in longitudinal waves  , as sound waves are longitudinal waves in which vibrations are in the direction of propagation of wave so they pass the polariser without any change and doesn't experience any polarization . 

Multiple choice physics world of sounds characteristics of sound wave time period, frequency and amplitude of sound sound waves are longitudinal waves

The frequency of a man's voice is $300Hz$ and its wavelength is $1$ meter. If the wavelength of a child's voice is $1.5m$, then the frequency of the child's voice is:

  1. $200Hz$
  2. $150Hz$
  3. $400Hz$
  4. $350Hz$
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

We know that ,

$f=\dfrac{c}{\lambda}$
So,
$\dfrac{f _{man's voice}}{f _{child's voice}}=\dfrac{\dfrac{c}{\lambda _{man's voice}}}{\dfrac{c}{\lambda _{child's voice}}}$
$\dfrac{f _{man's voice}}{f _{child's voice}}$=$\dfrac{\lambda _{child's voice}}{\lambda _{man's voice}}$     
$\dfrac{300}{f _{child's voice}}=\dfrac{1.5}{1}$
$f _{child's voice}=\dfrac{300}{1.5}$
$f _{child's voice}=200 Hz$
  

Multiple choice physics world of sounds characteristics of sound wave time period, frequency and amplitude of sound sound waves are longitudinal waves

When you speak to your friend which of the following quantities have a unique value in the sound produced by both the boys?

  1. amplitude

  2. wave velocity

  3. frequency

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

Out of the given quantities , wave velocity has a unique value . Because both the friends are producing the sound in the same medium , and wave velocity depends upon medium , which is not changing here .

Amplitude of the sounds depends upon the energy given by any of the friends to sound , so it may change .
Frequency of sound depends upon the thickness of vocal cords of two friends , so it also may vary . Now wavelength $\lambda \propto 1/f$, for a constant velocity , when frequency $f$ changes , wavelength will also change .