Physics · 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

Which of the following statements about sound is / are incorrect?

  1. Sound needs a medium to travel.

  2. Sound is produced by vibrating objects.

  3. Speed of sound is maximum in gases, and least in solids.

  4. Sound of frequency below audible range is called infrasonic sound.

  5. Excessive sound in the environment causes noise pollution.
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

Speed of sound is maximum in solids, and least in gases.

Multiple choice physics wave motion reflection of waves

A sound wave of frequency $1360 Hz$ falls normally on a perfectly reflecting  wall.  The shortest distance from the wall at which the air particles have maximum amplitude of vibration is ($v = 340 m/s$)

  1. $25 cm$
  2. $6.25 cm$
  3. $62.5 cm$
  4. $2.5 cm$
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

$v=f\lambda$
$\lambda=\dfrac{340}{1360}=\dfrac{1}{4}=0.25m$
$=25cm$
As the end is a node, shortest distance at which antinode is formed is $\dfrac{\lambda}{4}=6.25cm$

Multiple choice physics superposition and interference of sound waves

Consider ten identical sources of sound all giving the same frequency but having phase angles which are random. If the average intensity of each source is $I _{0}$, the average of resultant intensity $I$ due to all these ten sources will be

  1. $I = 100\ I _{0}$
  2. $I = 10\ I _{0}$
  3. $I = I _{0}$
  4. $I = \surd {10}\ I _{0}$
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

For incoherent sources (random phases), the intensities add linearly. If there are 10 sources each with intensity I0, the total intensity is 10 * I0.