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 physics study of sound determination of speed of sound by echo problems on sound sound needs a medium

A boy shouts while standing in front of a hill. He hears an echo after 6 sec. If the speed of sound  in air is 340 m/s. What is the distance of the hill from the position of the body?

  1. 519 m

  2. 1020 m

  3. 2040 m

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

Let distance of hill from the position of the body = d
Echo is heard after 6 sec
$d = v \dfrac{t}{2}$
$= \dfrac{(340 \times 6)}{2}$
$= 1020 m$

Multiple choice physics study of sound determination of speed of sound by echo problems on sound sound needs a medium

A sonar echo takes 8.8 s to return from a shack. How far away is the shack?

Given speed of sound in sea-water = 1533 m/s

  1. 348 m

  2. 5720 m

  3. 6745 m

  4. 13490 m
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

Let $d$ be the distance of shack from the sonar . Therefore  distance covered by sound to come back to sonar after reflection from shack ,  $=d$ ,

given , speed of sound in sea water $v=1533m/s  ,  t=8.8s$ ,
we have , distance=speed$\times time$ ,
               $d=v\times t=1533\times8.8$ ,
or            $d=13490.4m$

Multiple choice physics medical imaging ultrasonic sound using ultrasound in medicine ultrasound and its applications

The ultrasound waves can penetrate into matter to a large extent because they have 

  1. very high speed

  2. very high frequency

  3. very high wavelength

  4. very high amplitude
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation
The ultrasound waves can penetrate into matter to a large extent because they have very high frequency. They have frequency greater than 20,000 Hz.
Multiple choice physics medical imaging ultrasonic sound using ultrasound in medicine ultrasound and its applications

Fill in the blank. 

Sound wave in the  ______ range are best for reflecting off of small objects.

  1. Ultrasound

  2. Infrared

  3. Acoustic

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

Ultrasound has higher frequency than the audible range sound, and thus it has shorter wavelength. Due to this short wavelength, it becomes easy for it to interact(reflect, disperse) from small objects in its path.

Multiple choice physics medical imaging ultrasonic sound using ultrasound in medicine ultrasound and its applications

Three different vibrating objects produce three types of sounds X, Y and Z. Sounds X and Y cannot be heared by a man having normal range of hearing but sound Z can be heard easily. The sound X is used in hospital to break kidney stones of a patient into fine grains which then get flushed out with Urine. The sound similar to that which is produced during an earthquake before the main shock wave is generated.Name one device in our homes
which can produce sound like Z.

  1. oven

  2. Doorbell

  3. no such device is there in our homes

  4. all devices produce such sound
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

ultrasound is used for removing kidney stones.when ultrasound are targeted on such stone,the stones start vibrating at high frequency.the stone due to this vibratory motion. Breakdown into fine particles.ultrasounds and infrasounds are not audible to man.ultrasound have frequency more than 20kHz.a doorbell can produce an audible sound. Infrasound have frequency below 20Hz, X is ultrasound. Y is infrasound, Z is audible sound.

Multiple choice physics medical imaging ultrasonic sound using ultrasound in medicine ultrasound and its applications

Rats also play games by producing -------

  1. ultrasound

  2. infrasound

  3. audible sound

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

Frequencies higher than 20 kHz are called ultrasonic sound
or ultrasound. Ultrasound is produced by dolphins, bats and porpoises. Moths of certain families have very sensitive hearing equipment. These moths can hear the high frequency squeaks of the bat and know when a bat is flying nearby, and are able to escape capture. Rats also play games by producing ultrasound.

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 thunder is heard a few seconds after the flash is seen. This is because:

  1. speed ofsound is greater than speed oflight

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

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

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

It is because light travels faster  ($3\times10^{8}m/s$) than sound ($332m/s$) , so we hear thunder after a few second of the flash .