Question

A bumblebee buzzes past you at 3 m/s. The frequency of the hum made by its wings is 152 Hz. Assume the speed of sound to be 342 m/s. What is the observed frequency of the hum as the bumblebee approaches you?
155 Hz
153 Hz
150 Hz
149 Hz

Answer 1

Answer: 153 Hz

Explanation:

The apparent frequency heard by the listener is given by Doppler effect which states that apparent frequency heard by listener varies if the there is relative motion between the source and the listener.

In the given situation, observer is stationary and source of sound is approaching the listener. Thus,

$f_o=f_s(\frac{v}{v-v_s})$

$f_s=152 Hz\\ v = 342 m/s \\ v_s = 3 m/s$

$\Rightarrow f_o = 152 Hz (\frac{342m/s}{(342-3)m/s} )= 153 Hz$

Answer 2

It is 153 Htz I hope that helps :)