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NEET2019PhysicsDual Nature of MatterActual

Assertion: The relative velocity of two photons travelling in opposite direction is the velocity of light. Reason : The rest mass of photon is zero.

Options

  1. AIf both assertion and reason are true 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 both assertion and reason are false.

Correct answer

B. If both assertion and reason are true but reason is not the correct explanation of assertion.

Step-by-step solution

Velocity of first photon =u=c Velocity of second photon =v=-c Now, relative velocity of first photon with respect to second photon = u-v 1- u v c^2 = c-(-c) 1- (c)(-c) c^2 = 2 c 1+ c^2 c^2 = 2 c 1+1 = 2 c 2 =c Also the rest mass of photon is zero.

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