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JEE Main202311 Apr 2023Evening ShiftPhysicsWaves and SoundActual

A car P travelling at 20 m s - 1 sounds its horn at a frequency of 400 Hz . Another car Q is travelling behind the first car in the same direction with a velocity 40 m s - 1 . The frequency heard by the passenger of the car Q is approximately [Take, velocity of sound = 360 m s - 1 ]

Options

  1. A421   Hz
  2. B471   Hz
  3. C485   Hz
  4. D514   Hz

Correct answer

B. 471   Hz

Step-by-step solution

Let velocity of sound in air be v   m   s - 1 . Using Doppler formula, f = f 0 v + v o v - v s = f 0 v + 40 v - 20 = 400 360 + 40 340 ≈ 471   Hz

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