The observer is moving with velocity $v_0^{}$ towards the stationary source of sound and then after crossing moves away from the source with velocity $v_0^{}\mathrm{ }.$ Assume that the medium through which the sound waves travel is at rest. If $v$ is the velocity of sound and $n$ is the frequency emitted by the source then the difference between apparent frequencies heard by the observer is

• Correct answer
  A

  $\frac{2n v_0}{v}$
• B

  $\frac{n v_o}{v}$
• C

  $\frac{v}{2n v_o}$
• D

  $\frac{v}{n{v}_o}$

Hence, the correct answer is option: 'A'.