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NEET 2000 (AIPMT) · Doppler Effect

Doppler Effect question from NEET 2000 (AIPMT)

Q81NEET 2000 · AIPMTEasy

Doppler Effect

Two stationary sources each emitting waves of wavelength λ\lambda, an observer moves from one source to another with velocity u. Then number of beats heard by him

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Answer: (a)

  1. Source frequency f=v/λf = v/\lambda.
  2. Approaching one source: f v+uvf\,\dfrac{v+u}{v}; leaving the other: f v−uvf\,\dfrac{v-u}{v}.
  3. Beats =2fuv=2uλ= \dfrac{2fu}{v} = \dfrac{2u}{\lambda}
  4. So the answer is (a) 2uλ\dfrac{2u}{\lambda}.
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