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MHT CET20242 May 2024Evening ShiftPhysicsWaves and SoundActual

The driver of a car travelling with a speed ' V ₁ ' m / s towards a wall sounds a siren of frequency ' n ' Hz. If the velocity of sound in air is ' V ' m / s , then the frequency of the sound reflected from the wall and as heard by the driver in Hz is

Options

  1. A( V₁ V-V₁ ) n
  2. B( V₁-V V+V₁ ) n
  3. C( V+V₁ V-V₁ ) n
  4. D( V-V₁ V+V₁ ) n

Correct answer

C. ( V+V₁ V-V₁ ) n

Step-by-step solution

For the source moving towards the wall, n ₁= n [ ~V ~V - V ₁ ] For the reflected sound waves, the driver acts as an observer moving towards the wall array ll & n ₂= n ₁ [ ~V + V ₁ ~V ] & n ₂= [ V + V ₁ ~V ] [ V ~V - V ₁ ] n & n ₂= n [ ~V + V ₁ ~V - V ₁ ] array

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