Question

Hiran is standing beside the road when he hears a bird flying away from hip and chirping. The bird’s chirp has a frequency of 1800hz, and the bird flying away from him at 6m/s. What frequency does hiran hear? Assume the temperature is 20 Celsius.

Answer 1

The frequency of bird chirping hear by hiran will be 1.77 kHz.

Explanation:

As per Doppler effect, the observer will feel a decrease in the frequency of the receiving signal if the source is moving away from the observer. So the shifted frequency is obtained using the below equation:

$f'=\frac{c}{c+v_{s} }f$

Here , c is the speed of sound, Vs is the velocity of source with which it is moving away. f is the original frequency of source and f' is the frequency shift heard by the observer.

As here, f = 1800 Hz, Vs= 6 m/s and c = 343 m/s, then

$f'=\frac{343}{343+6} \times 1800=1.77\ kHz$

So, the frequency of bird chirping hear by hiran will be 1.77 kHz.