Question

Compare the apparent frequencies of a 2450 Hz source moving away from you at 25m/s and when you are moving away from the source at 25mLs

Answer 1

Given:

$f_0=2450\:\rm Hz$

$v=25\:\rm m/s$

The Doppler effect equation is given by

$$f=f_0\left(\frac{c\pm v_r}{c\pm v_s}\right)$$

(i) source moving away:

$$f=f_0\left(\frac{c}{c+ v_s}\right)=2450\left(\frac{340}{340+ 25}\right)=2282\:\rm Hz$$

(ii) you are moving away from the source:

$$f=f_0\left(\frac{c-v_r}{c}\right)=2450\left(\frac{340-25}{340}\right)=2270\:\rm Hz$$