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A train moves towards a stationary observer with speed 34 m s - 1 . The train sounds a whistle and its frequency registered by the observer is v 1 . If the train's speed is reduced to 17 m s - 1 , the frequency registered is v 2 . If the speed of sound is 340 m s - 1 , then the ratio v 1 v 2 is

Options

  1. A2
  2. B1 2
  3. C18 19
  4. D19 18

Correct answer

D. 19 18

Step-by-step solution

Perceived frequency by observer in Ist case v 1 = v v v - v s ∴       v 1 = v 340 340 - 34 = 340 v 306 Perceived frequency by observer in IInd case v 2 = v 340 340 - 17 = 340 v 323 Therefore, v 1 v 2 = 340 v 306 × 323 340 v = 323 306 = 19 18

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