Question

If an observer moves towards a stationary source, then the apparent frequency is given by:

• A. \( f' = f_0 \left(\frac{v+v_o}{v}\right) \)
• B. \( f' = f_0 \left(\frac{v-v_o}{v}\right) \)
• C. \( f' = f_0 \left(\frac{v}{v+v_o}\right) \)
• D. \( f' = f_0 \left(\frac{v}{v-v_o}\right) \)

Hint:

Moving towards \(\Rightarrow\) frequency increases \(\Rightarrow\) use + sign.

Answer 1

The Correct Option is A

Concept: Doppler effect for moving observer: \[ f' = f_0 \left(\frac{v \pm v_o}{v}\right) \]

Step 1: Observer moving towards source.
Use plus sign.

Step 2: Final expression.
\[ f' = f_0 \left(\frac{v+v_o}{v}\right) \]