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NTA Abhyas JEE Main2020PhysicsWaves and SoundPractice

A sound wave of frequency f propagating through the air at a speed c is reflected from a surface which is moving away from the source with a constant speed v . The frequency of the reflected wave as perceived by the observer at the position of the source will be

Options

  1. Af ( c + 2 v ) c + v
  2. Bf ( c + v ) c - v
  3. Cf ( c - v ) c + v
  4. Df ( c - v ) c - 2 v

Correct answer

C. f ( c - v ) c + v

Step-by-step solution

In the first case observer (surface) is moving away, so the perceived frequency is f ′ = f ( c − v c ) In the second case source (surface) is moving away, so the perceived frequency is f ″ = f ′ ( c c + v ) = f ( c − v c + v )

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