Waves - Result Question 78
80. 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 $300 m / s$ )
[1998]
(a) $n_1=10 n$
(b) $n_1=0$
(c) $n_1=0.1 n$
(d) $n_1=-0.1 n$
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Answer:
Correct Answer: 80. (b)
Solution:
- (b) As the source is not moving towards or away from the observer in a straight line, so the Doppler’s effect will not be observed by the observer.
If source and observer both are relatively at rest and if speed of sound is increased then frequency heard by observer will not change.
