Question
Physics Question on Waves
A whistle giving out 450 Hz approaches a stationary observer at a speed of 33 m/s. The frequency heard by the observer (in Hz) is (Speed of sound = 330 m/s) .
A
409
B
429
C
517
D
500
Answer
500
Explanation
Solution
Source is moving towards the observer
\hspace10mm f'=f \bigg(\frac{v}{v-v_s}\bigg)= 450\bigg(\frac{330}{330-33}\bigg)
\hspace10mm f'= 500\, Hz