A listener is at rest with respect to the source of sound. A wind starts blowing along the line joining the source and the observer.

Monjur Alahi

A listener is at rest with respect to the source of sound. A wind starts blowing along the line joining the source and the observer. Which of the following quantities do not change ?

(a) Frequency.

(b) Velocity of sound .

(c) Wavelength.

(d) Time period.


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Salim Ahmed Kawsar

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(a) Frequency.

(d) Time period.

EXPLANATION: 

The sound wave propagate due to the vibrations of the particles of the medium (air), though the particles do not move with the wave. When the wind blows the vibrating particles also move with the wind speed. The velocity of the sound changes accordingly. Option (b) is not true. The frequency and hence the time period of the sound remains the same as that of the source. Options (a) and (d) are true.          

Frequency remaining the same the wavelength changes proportional to the sound velocity (=V/ν), hence (c) is not true.

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