Question

A source of sound is travelling with a velocity of 30 m/s towards a stationary observer. If actual frequency of source is 1000 Hz and the wind is blowing with velocity 20 m/s in a direction at ${60}^{\circ }$ with the direction of motion of source, then the apparent frequency heard by observer is (speed of sound is 340 m/s)

• A. 1011 Hz
• B. 1000 Hz
• C. 1094 Hz
• D. 1086 Hz

Answer 1

The correct option is C 1094 Hz

$f=\left(\frac{v+v_m}{v+v_m-v_{source}}\right)1000$
$=\left(\frac{340+20cos{60}^{\circ }}{340+20cos{60}^{\circ }-30}\right)1000$
=1094 Hz