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 propagation of sound waves longitudinal vs transverse wave sound and light comparison of speed of sound with speed of light

Two waves of wavelengths $\lambda$ and $(\lambda + \triangle \lambda)$ produce $6$ beats per second. If $\dfrac {\triangle \lambda}{\lambda} = \dfrac {\lambda + \triangle \lambda}{51}$, find the speed of sound wave in a gas in which these waves produce beats?

  1. $316\ m/s$
  2. $310\ m/s$
  3. $306\ m/s$
  4. $326\ m/s$
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

Beat frequency = 6 Hz. v = f * lambda. Using the relationship between wavelength change and beats, the calculation leads to 326 m/s.

Multiple choice physics propagation of sound waves longitudinal vs transverse wave sound and light comparison of speed of sound with speed of light

Flash and thunder are produced simultaneously. But the thunder is heard a few seconds after the flash is seen. Why?

  1. The speed of sound is greater than the speed of light.

  2. The speed of sound is equal to the speed of light.

  3. The speed of light is greater than the speed of sound.

  4. The speed of light is less than the speed of sound.
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

Flash and thunder are produced simultaneously. But the flash is seen first and then the sound is heard. This is because the speed of sound in air is very less than the speed of light in air.

Speed of sound in air $=334\,m/s$
Speed of light in air $=3\times 10^8\,m/s$

Multiple choice physics propagation of sound waves longitudinal vs transverse wave sound and light comparison of speed of sound with speed of light

The time interval between a lightning flash and the first sound of thunder was found to be $5 \ s$. If the speed of sound in air is $330  \ ms^{-1}$, find the distance of flash from the observer.

  1. $1650 \ m$
  2. $165 \ m$
  3. $330 \ m$

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

The speed of the sound, distance traveled and the time taken relationship is given as follows.


$Speed\; of\; sound=\dfrac { Distance\; travelled}{ Time\; taken} $

From this equation the Distance traveled is derived as 
$Distance\; travelled=Speed\; of\; sound\times Time\; taken$


That is, $Distance\; travelled=330\; m/s\times 5\; seconds$, given that the speed of sound is 330 m/s.

= 1650 meters.

Hence, the distance of flash from the observer is 1650 meters.

Multiple choice physics propagation of sound waves longitudinal vs transverse wave sound and light comparison of speed of sound with speed of light

When a tuning fork of 500 Hz is used, the first and second resonating lengths of closed air column are found to be 18 cm and 54 cm respectively. Find the velocity of sound in S.I. system.

  1. $120{ms}^{-1}$
  2. $240{ms}^{-1}$
  3. $360{ms}^{-1}$
  4. $480{ms}^{-1}$
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

For a closed pipe, the resonance lengths are L1 = lambda/4 and L2 = 3*lambda/4. The difference L2 - L1 = lambda/2, so lambda = 2 * (54 - 18) = 72 cm = 0.72 m. Velocity v = f * lambda = 500 * 0.72 = 360 m/s.

Multiple choice physics propagation of sound waves longitudinal vs transverse wave sound and light comparison of speed of sound with speed of light

The frequency of fundamental mode of vibration of an air column enclosed in a closed end pipe is 250 Hz. If its length is 33 cm, then find the velocity of sound in air.

  1. $390 {ms}^{-1}$
  2. $160 {ms}^{-1}$
  3. $330 {ms}^{-1}$
  4. $150 {ms}^{-1}$
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

For a closed pipe, the fundamental frequency f = v / (4 * L). Given f = 250 Hz and L = 33 cm = 0.33 m, v = f * 4 * L = 250 * 4 * 0.33 = 1000 * 0.33 = 330 m/s.

Multiple choice business economics and quantitative methods measures of dispersion and skewness shortcut method for calculating mean deviation about mean mean deviation about mean and median range and mean deviation

A frequency distribution having two modes is said to be ________.

  1. unimodal

  2. bimodal

  3. trimodal

  4. without mode
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

A frequency distribution with two modes is called bimodal. Unimodal has one mode, and trimodal has three.

Multiple choice business economics and quantitative methods measures of dispersion and skewness shortcut method for calculating mean deviation about mean mean deviation about mean and median range and mean deviation

Mode is that value in a frequency distribution which possesses __________.

  1. minimum frequency

  2. maximum frequency

  3. frequency one

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

By definition, the mode of a frequency distribution is the value that occurs most frequently, meaning it has the maximum frequency.

Multiple choice physics communication system commonly used terms in electronic communication system elements of communication system electromagnetic waves and communication system

A transducer used at the transmitting end, serves the purpose of converting

  1. electrical signal to sound form

  2. sound signal to electrical form

  3. electrical signal to magnetic form

  4. sound signal to magnetic form
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

In this case transducer takes the sound signal and convert them to electrical signal.

Multiple choice physics communication system commonly used terms in electronic communication system elements of communication system electromagnetic waves and communication system

During the process of modulation the RF wave is called

  1. Modulating wave

  2. Modulated wave

  3. Carrier wave

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

Signals which need to be transferred are superimposed on high frequency wave, which is called carrier wave, as the name suggests it carries the signals.

Multiple choice physics communication system commonly used terms in electronic communication system elements of communication system electromagnetic waves and communication system

A transducer used at the transmitting end, serves the purpose of converting

  1. electrical signal to sound form

  2. sound signal to electrical form

  3. electrical signal to magnetic form

  4. sound signal to magnetic form
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

The message from the information source may not be in electrical form, so to convert these information, i.e., in form of sound to electrical form, a transducer like a microphone is used.

Multiple choice physics communication system commonly used terms in electronic communication system elements of communication system electromagnetic waves and communication system

"Man-made" noise can come from:

  1. equipment that sparks

  2. temperature

  3. static

  4. all of the above
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

Man-made noise is a noise created due to wear and tear of electrical machinery used in transmission systems. They are due to the type of amplifiers (class B) type of pulses (wideband pulses), often caused by ignition circuits, lightning, and switching elements causing spark gaps

Multiple choice physics communication system commonly used terms in electronic communication system elements of communication system electromagnetic waves and communication system

During the process of transmission and reception, the signal gets deteriorated due to

  1. noise introduced in the system

  2. distortion in the system

  3. both (A) and (B)

  4. neither (A) nor (B)
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

Noise is the unwanted energy and distortion both occurring at various stage of a system leads to deterioration of signal, as signal to noise ratio becomes so poor that signal becomes unintelligible and useless.