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JEE Main20199 Apr 2019Evening ShiftPhysicsWaves and SoundActual

Two cars A and B are moving away from each other in opposite directions. Both the cars are moving with speed of 20 m s - 1 with respect to the ground. If an observer in car A detects a frequency 2000 H z of the sound coming from car B, what is the natural frequency of the sound source in car B? (speed of sound in air = 340 m s - 1 )

Options

  1. A2150 H z
  2. B2300 H z
  3. C2250 H z
  4. D2060 H z

Correct answer

C. 2250 H z

Step-by-step solution

From Doppler effect: f ' = V ∓ V 0 V ± V S f 0 2000 = 340 - 20 340 + 20 f 0 = 320 360 f 0 f 0 = 9 8 × 2000 = 2250 H z

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