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

Which one of the following is correct? Echo-location was first discovered in

Directions: Read the passage and answer the question.

Not all sounds made by animals serve for communication, and we have only to turn to that extraordinary discovery of echo - location in bats to see a case in which the voice plays a strictly utilitarian role. To get a full appreciation of what this means we must turn first to some recent human inventions. Everyone knows that if a person shouts in the vicinity of a wall or mountain side, an echo will come back. The further off this solid obstruction, the longer time will elapse for the return of the echo. A sound made by tapping on the hull of a ship will be reflected from the sea bottom, and by measuring the time interval between the taps and the receipt of the echoes, the depth of the sea at that point can be calculated. So was born the echo - sounding apparatus, now in general use in ships. Every solid object will reflect a sound, varying according to the size of and nature of the object. A shoal of fish will do this. So it is a comparatively simple step from locating the sea bottom to locating a shoal of fish. With experience, and with improved apparatus, it is now possible not only to locate a shoal, but to tell if it is herring, cod, or other well - known fish, by the pattern of its echo. A few years ago it was found that certain bats emit squeaks and by receiving the echoes they could locate and steer clear of obstacles or locate flying insects on which they feed. This echo - location in bats is often compared with radar, the principle of which is similar.

  1. bats

  2. cods

  3. navigation

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

Line 2 of the passage.

Multiple choice

In sonography, wavelength of ultrasound used is

  1. 20,000 Hz/sec

  2. 40-50 kHz/sec

  3. 1-15 MHz

  4. 1500-2000 MHz
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

Medical ultrasound imaging uses frequencies in the megahertz range, typically 1-15 MHz. Higher frequencies provide better resolution but less tissue penetration. Options A and B have incorrect units and are too low, while D is too high for diagnostic imaging.

Multiple choice

The speed of the sound is more in which of the following?

  1. Steel

  2. Hydrogen

  3. Water

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

Sound waves require a medium to travel and their speed depends on the density and elasticity of that medium. Sound travels significantly faster in solids like steel than in liquids or gases because the particles are more closely packed.

Multiple choice

The potential arising due to the propagation of ultrasound through a fluid containing ions and either solid particles or emulsion droplets ?

  1. Ion Vibration Current/Potential

  2. Streaming Vibration Current/Potential

  3. Colloid vibration current

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

Colloid vibration current is an electroacoustic phenomenon that arises when ultrasound propagates through a fluid that contains ions and either solid particles or emulsion droplets .The pressure gradient in an ultrasonic wave moves particles relative to the fluid. This motion disturbs the double layer that exists at the particle-fluid interface.

Multiple choice

You will hear a recording about the brain. At the end of the recording, the last word or group of words has been replaced by a beep. Select the correct option to complete the recording.

  1. ignored people speaking

  2. participated in conversations

  3. understood spoken language

  4. understood foreign languages
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

The text is about how the brain works and, in particular, how different areas of the brain perform different functions. It describes a patient who had damage to one part of the brain. This affected his ability to talk, but not his ability to understand. So, the missing words are: understood spoken language.

Multiple choice

A dog barks in a park and hears its echo after 0.5 seconds. If the sound of its bark got reflected by a nearby building, then the distance between the dog and the building is (assume the sound of speed in air is 346 m/s)

  1. 86.50 m

  2. 80.60 m

  3. 75.00 m

  4. 8.65 m
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

2d = v x t, where d is the distance to be calculated, v is the speed of sound and t is the time taken to hear the echo 2d = 346 x 0.5 d = 346 x 0.5/2 = 86.50 m

The correct answer is option (1).

Multiple choice

The loudness of a sound depends on

  1. frequency

  2. amplitude

  3. wavelength

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

The loudness of a sound depends on amplitude of sound. Frequencies, wavelength and time period are the characteristics of sound. Hence, option 2 is correct.