Question

In Doppler effect, when a source moves towards a stationary observer, the apparent increase in frequency is due to

• A. increase in wavelength of sound received by observer
• B. decrease in wavelength of sound received by observer
• C. increase in number of waves received by observer in one second
• D. decrease in number of waves received by observer in one second

Answer 1

The correct option is B decrease in wavelength of sound received by observer

Change of frequency due to the Doppler effect is :

$\overline{n}=n\left(\frac{v}{v-v_s}\right)$. So, $\overline{n}>n$, So increase in the frequency.

Now, frequency is inversely proportional to the wavelength, so in this case the wavelength will decrease.