Question

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 :

• A. 409
• B. 429
• C. 517
• D. 500

Answer 1

The correct option is D

500

Source is moving towards the observer $f^{\prime }=f=(\frac{v}{v-v_s})=450(\frac{330}{300-33})$

$f^{\prime }=500Hz$