doppler effect (source moving)

Question

Source approaches stationary observer. Observed frequency?

RankGuru · Accepted Answer

1. **Doppler Effect**: The change in observed frequency due to the relative motion between the source and the observer.
2. **Physical Mechanism**: As the source moves toward the observer, each successive wave crest is emitted from a position closer to the observer than the previous one.
3. **Wavelength Compression**: This effectively 'squeezes' the waves, reducing the apparent wavelength ($\lambda' = \lambda - v_s/f$).
4. **Frequency Shift**: Since $v = f'\lambda'$, a smaller wavelength leads to a **higher frequency** ($f' > f$).
5. **Formula**: $f' = f \left(\frac{v}{v - v_s}\right)$, where $v$ is the speed of sound and $v_s$ is the source speed toward the observer.

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doppler effect (source moving)

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