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JEE Main201912 Apr 2019Morning ShiftPhysicsWaves and SoundActual

A submarine A travelling at 18 km hr - 1 is being chased along the line of its velocity by another submarine B travelling at 27 km hr - 1 . B sends a sonar signal of 500 H z to detect A and receives a reflected sound of frequency v . The value of v is closed to (Speed of sound in water 1500 m s - 1 )

Options

  1. A504 H z
  2. B499 H z
  3. C502 H z
  4. D507 H z

Correct answer

C. 502 H z

Step-by-step solution

V A = 18   km   h - 1 = 5   m   s - 1 ; V B = 27   km   h - 1 = 7 .5 m   s - 1 Frequency received by A , f A = f 0 1500 - 5 1500 - 7 .5 Frequency of reflected wave as heard by B . f ' B = f A 1500 + 7 .5 1500 + 5 = f 0 1500 - 5 1500 - 7.5 1500 + 7.5 1500 + 5 = 500 1495 1492.5 1507.5 1505 = 501.67   H z ≈ 502   Hz

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