Tag: acoustics

Questions Related to acoustics

among the following, what is the most important practical application of microwave?

physics acoustics reverberation applications of reflection of sound multiple reflection of sound and reverberation

  1. Microwave oven

  2. TV

  3. Radar

  4. Radio-astronomy

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Correct Option: C

RADAR is used for

physics acoustics reverberation applications of reflection of sound multiple reflection of sound and reverberation

  1. locating submerged submarines

  2. receiving a signals in a radio receiver

  3. locating geostationary satellites

  4. detecting and locating the position of objects such as aeroplanes

Show answer
Correct Option: D
Explanation:

Radar is an acronym fro RAdio Detection And Ranging

$\rightarrow$ It is basically a detection system that uses radio waves to determine the range, angle or velocity of objects.
$\rightarrow$ More over; used for distance measurement
$\rightarrow$ Hence; can be used for detecting and locating the position of objects like aero planes

RADAR makes the use of.

physics acoustics reverberation applications of reflection of sound multiple reflection of sound and reverberation

  1. Infra-red waves of shorter wavelengths

  2. Radio-waves of very short wavelength

  3. Radio-waves of very long wavelength

  4. Ultraviolet waves of longer wavelengths

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Correct Option: B

A rocket is moving at a speed of $220\,\,m\,\,s^{-1}$ towards a stationary target, emits a sound of frequency  $1000 Hz$. Some of the sound reaching the target gets reflected back to the rocket as echo. The frequency of the echo as detected by the rocket is
(Take velocity of sound $= 330\,\,m\,\,s^{-1}$)

physics acoustics reverberation applications of reflection of sound multiple reflection of sound and reverberation

  1. $3500 Hz$

  2. $4000 Hz$

  3. $5000 Hz$

  4. $3000 Hz$

Show answer
Correct Option: C
Explanation:

As the source (i.e rocket) is moving toward the stationary target, therefore the frequency of sound detected by the target is
$\upsilon' = \dfrac{\upsilon _0\nu}{\nu - \nu _s} = \dfrac{1000 \times 330}{330 - 220} = \dfrac{1000 \times 330}{110} = 3000 Hz$
Now the target is the source (as it is the source of echo) and the rocket's detector is the observer who intercepts the echo of frequency \acute{\upsilon}. Hence, the frequency of the echo detected by the rocket is


$\upsilon" = \dfrac{\upsilon'(\nu + \nu _O)}{\nu} = \dfrac{3000(330 + 220)}{330} = 5000 Hz $