Q70 / 90 · JEE Main 2012 (12 May Online) · Physics

This question has Statement 1 and Statement 2 . Of the four choices given after the Statements, choose the one that best describes the two Statements. Statement 1: Bats emitting ultrasonic waves can detect the location of a prey by hearing the waves reflected from it. Statement 2: When the source and the detector are moving, the frequency of reflected waves is changed.

  • A
    Statement 1 is false, Statement 2 is true.
  • B
    Statement 1 is true, Statement 2 is false.
  • Correct answer
    C
    Statement 1 is true, Statement 2 is true, Statement 2 is not the correct explanation of Statement 1.
  • D
    Statement 1 is true, Statement 2 is true, Statement 2 is the correct explanation of Statement 1.

Solution

Bats catch the prey by hearing reflected ultrasonic waves. When the source and the detector (observer) are moving, frequency of reflected waves change. This is according to Doppler's effect.

Hence, the correct answer is option: 'C'.

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