Question

A vehicle, with a horn of frequency n is moving with a velocity of 30m/s in a direction perpendicular to the straight line joining the observer and the vehicle. the observer perceives the sound to have a frequency n+n1 .then n1 is equal to

Answer 1

Ans is : By Doppler effect, the apparent change in frequency of wave due to the relative
motion between the source of waves and observer.
If
vl​ = velocity of the listener
vs = velocity of the source
v = velocity of sound
n= frequency of sound reaching from the source to the listener.
n1= Apparent frequency (i.e. Changed frequency due to movement of source and
listener)

n

1

= (

v−

v

1

v−

v

s

)×n



But in our case, the source and observer move at right angles to each other. The
Doppler Effect is not observed when the source of the sound and the observer are
moving at right angles to each other.
So, if n = original frequency of sound the observer will perceive the sound with a
frequency of n (because of no Doppler effect).
Hence the
n1 = change in frequency = 0.

Answer 2

Answer:

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