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NTA Abhyas JEE Main2020PhysicsWaves and SoundPractice

A sound source emitting sound of frequency 450 Hz is approaching a stationary observer with velocity 30 m s - 1 and another identical source is going away from the observer with the same velocity. If the velocity of sound is 330 m s - 1 , then the difference of frequencies heard by observer is

Options

  1. A103 . 5   Hz
  2. B82 . 5 Hz
  3. C33 . 5 Hz
  4. D92 . 5 Hz

Correct answer

B. 82 . 5 Hz

Step-by-step solution

f 1 = v v - v s f 0 = 330 330 - 30 × 450 f 1 = 330 300 × 450 = 11 × 4 5 f 1 = 495 H z f 2 = 330 360 × 450 f 2 = 412.5 H z Δ f = 82.5 H z

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