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

Step-by-step solution

Key Idea Apply Doppler's effect. Whenever there is a relative motion between a source of sound and the observer (listner), the frequency of sound heard by the observer is different from the actual frequency of sound emitted by source. [for case I] n ^ = v v -30 n [for case II] n^ = v+30 v n^ From Eqs. (i) and (ii), we get aligned n ^ = v +30 v -30 n & = 360 300 600 & =720 ~Hz aligned