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 study of sound sound as a wave of disturbance vibrations in a tuning fork vibrations in tuning fork

Which of the following are true.

  1. the sound and light waves both are longitudinal waves

  2. both the sound and light waves are transverse

  3. in air ,the sound waves are longitudinal as well as transverse

  4. in air, the sound waves are longitudinal and the light waves are transverse
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

Longitudinal waves are always characterized by particle motion being parallel to wave motion. A sound wave travelling through air is a classic example of a longitudinal wave. Transverse wave moves perpendicular to the direction of wave motion. Light waves are transverse in nature.

Multiple choice physics study of sound sound as a wave of disturbance vibrations in a tuning fork vibrations in tuning fork

Compressions and rarefactions are seen in

  1. longitudinal and transverse waves

  2. longitudinal waves only

  3. transverse waves only

  4. none
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

   Longitudinal waves propagate in a medium in the form of compressions and rarefactions . When pressure becomes high , medium particles come closer and a compression is formed and due to low pressure , rarefaction is formed .

  Transverse waves propagate in the form of crests and troughs .

Multiple choice physics study of sound sound as a wave of disturbance vibrations in a tuning fork vibrations in tuning fork

Sound is called longitudinal wave because

  1. sound need a material medium for propagation

  2. the molecules of the medium oscillate to and fro about their mean position in the direction of propagation

  3. sound waves moves in the direction of its production

  4. all reasons are correct
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

When a sound travels through their medium, the molecules in the air oscillate to and fro about their mean positions in the direction of propagation of sound wave.

Multiple choice physics study of sound sound as a wave of disturbance vibrations in a tuning fork vibrations in tuning fork

Compressions and rarefactions are seen in :

  1. longitudinal and transverse waves

  2. longitudinal waves only

  3. transverse waves only

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

In case of longitudinal waves compressions and rarefactions are seen. Compressions are the regions of high density and rarefactions are regions of low density.In transverse waves generally crest and troughs are seen.

Multiple choice physics study of sound sound as a wave of disturbance vibrations in a tuning fork vibrations in tuning fork

When sound travels through air, the air particles :

  1. vibrate along the direction of wave propagation

  2. vibrate but not in any fixed direction

  3. vibrate perpendicular to the direction of wave propagation

  4. do not vibrate
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

Sound is a longitudinal wave.  If the particles of a medium vibrate or oscillate to and fro about their equilibrium position along the direction of propagation of disturbance then the wave is called longitudinal wave.

Multiple choice physics study of sound sound as a wave of disturbance vibrations in a tuning fork vibrations in tuning fork

Which of the following is true?

  1. The sound and light waves both are longitudinal waves

  2. Both the sound and light waves are transverse

  3. In air ,the sound waves are longitudinal as well as transverse

  4. In air, the sound waves are longitudinal and the light waves are transverse
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

If the particles of a medium vibrate or oscillate to and fro about their equilibrium position along the direction of propagation of disturbance then the wave is called longitudinal wave.

Multiple choice physics study of sound sound as a wave of disturbance vibrations in a tuning fork vibrations in tuning fork

The sound propagates in a gaseous medium by

  1. Transverse waves

  2. Longitudinal waves

  3. Both (a) and (b)

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

For transverse wave, cohesion is an important property in the medium through which the wave energy can be transported. Gas does not have such a cohesion property. Hence there is no chance for transverse waves to be propagated through gas medium. So the sound propagates in a gaseous medium by longitudinal wave.

Multiple choice physics study of sound sound as a wave of disturbance vibrations in a tuning fork vibrations in tuning fork

Fill in the blank. 

Sound waves in air are __________waves.

  1. Longitudinal

  2. Radial

  3. Transverse

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

Longitudinal waves are waves in which the motion of the individual particles of the medium is in a direction that is parallel to the direction of energy transport. Sound waves in air (and any fluid medium) are longitudinal waves because particles of the medium through which the sound is transported vibrate parallel to the direction that the sound wave moves.

Multiple choice physics study of sound sound as a wave of disturbance vibrations in a tuning fork vibrations in tuning fork

A uniform tub to length $60.5\,cm$ is held vertically with its lower end dipped in water. A sound source of frequency $500\,Hz$ sends sound waves into the tube. When it is $50\,cm$, the tube resonates with the source of sound. Two lowest frequencies (in Hz), to which tube will resonate when it is taken out of water, are (approximately)

  1. $281, 562$
  2. $281, 843$
  3. $276, 522$
  4. $272, 544$
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

When the tube is taken out of water, it acts as an open pipe of length L = 0.605 m. The fundamental frequency is f = v / (2L). Using the resonance data (50 cm length, 500 Hz source), the speed of sound is v = 4 * f * L_res = 4 * 500 * 0.5 = 1000 m/s. The fundamental frequency of the open pipe is 1000 / (2 * 0.605) = 826 Hz, which does not match the options well, suggesting a potential calculation error in the source question or specific assumptions about the end correction.

Multiple choice physics study of sound sound as a wave of disturbance vibrations in a tuning fork vibrations in tuning fork

If wind blows in a direction opposite to the sound propagation, then the velocity of the sound

  1. increases

  2. decreases

  3. remains constant

  4. Cannot be determined
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

When wind blows in the direction opposite to sound propagation, the effective velocity of the sound wave relative to the ground decreases. This is a standard application of the principle of relative velocity for waves in a moving medium.

Multiple choice physics study of sound sound as a wave of disturbance vibrations in a tuning fork vibrations in tuning fork

A replica of longitudinal waves can be best observed 

  1. by swinging a pendulum

  2. by pressing and releasing a horizontal spring

  3. by striking a guitar string

  4. by rotating a top
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

If we press and release a horizontal spring, it exhibits a confined motion of compression and rarefaction. So, it shows a replica of longitudinal waves. A swinging pendulum performs simple harmonic motion. A struck guitar string exhibits a replica of transverse waves. A rotating top exhibits rotational motion.