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MHT CET202525 Apr 2025Evening ShiftPhysicsWaves and SoundActual

At what speed should a source of sound move so that the observer finds the apparent frequency equal to half the original frequency?

Options

  1. AV 2
  2. B2 V
  3. CV 4
  4. DV

Correct answer

D. V

Step-by-step solution

The apparent frequency f' observed when a sound source moves away from a stationary observer is given by f' = f₀ ( V V + v_s ) . Given that f' = f₀ 2 , substitute into the equation: f₀ 2 = f₀ ( V V + v_s ) . Divide both sides by f₀ : 1 2 = V V + v_s . Solving for v_s : V + v_s = 2V v_s = V . The source must move at a speed equal to the speed of sound in the medium. The correct answer is D .

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