Question

When a source of sound is in motion towards a stationary observer, the effect observed is ________.

• A. decrease in the velocity of sound only
• B. increase in the frequency of sound only
• C. increase in the velocity of sound only
• D. increase in both the velocity and the frequency of sound

Answer 1

The correct option is B increase in the frequency of sound only

When the source of sound moves towards a stationary observer, the observed sound wave has lower wavelength, higher frequency but same velocity.

$f=\frac{v_{sound}}{v_{sound}-v_{source}}{f}_{source}$

So option B is correct.