Question

A source of sounds emitting waves of frequency 100 Hz and an observer O are located at same distance from each other The source is moving with a speed of 19.4 ms^-1 at an angle of 60° with the source-observer line as shown in the figure. The observer is at rest. The apparent frequency observed by the observer (velocity of sound in air 330 ms^-1 ) is ……

(a) 97 Hz 

(b) 100 Hz 

(c) 103 Hz 

(d) 106 Hz

Answer 1

(c) 103 Hz

\(f' = \frac{v}{v - v_s cos θ}\) 

= \(\frac{330}{330 - 19.4 cos 60º}\) x 100 

= 103 Hz