A vehicle, with a horn of frequency n is moving with a velocity of 30 m/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 + n_(1)`. Then (if the sound velocity in air is 300 m/s)

Options

A. `n_(1) = 10n`
B. `n_(1) = 0`
C. `n_(1) = 0.1n`
D. `n_(1) = -0. 1n`

Answer

B

Explanation

Doppler effect is not observed, when the source is moving perpendicular to the line joining the observer and the listener. Hence there is no apparent frequency.
`:.` The observer hears the real frequency
i.e., `n+ n_(1) = n or n_(1) = 0`