Question
The driver of a car travelling with speed 30 ms-1 towards a hill sounds a horn of frequency 600 Hz. If the velocity of sound in air is 330 ms-1, the frequency of reflected sound as heard by driver is
-
550 Hz
-
555.5 Hz
-
720 Hz
-
500 Hz
Solution
C.
720 Hz
Apply Doppler's effect.
Whenever there is a relative motion between a source of the sound and the observer (listener), the frequency of sound heard by the observer is different from the actual frequency of sound emitted by the source.
