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NEET
Exam
NEET
Subject
Physics
Chapter
Waves and Sound

NEET · Physics · Waves and Sound

Assertion: In Doppler effect, if the source is moving, change in...

Assertion: In Doppler effect, if the source is moving, change in frequency is observed due to change in wavelength. Reason : By the motion of source wavelength always decreases.

Options

  1. AIf both Assertion and Reason are correct and Reason is the correct explanation of Assertion.
  2. BIf both Assertion and Reason are true but Reason is not the correct explanation of Assertion.
  3. CIf Assertion is true but Reason is false.
  4. DIf Assertion is false but Reason is true.

Correct answer

C. If Assertion is true but Reason is false.

Step-by-step solution

When the source moves, the wavelength of sound waves changes (compressed if source approaches, stretched if source recedes). Since velocity of sound in medium is constant, frequency changes as (f= v / \lambda . \rightarrow) Assertion is correct. But wavelength does not always decrease, it decreases only when the source moves towards the observer, and increases if it moves away. (\rightarrow) Reason is incorrect. Final Answer: Assertion is True, Reason is False.
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