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NEET2005PhysicsThermal Properties of MatterActual

Assertion : A body that is a good radiator is also a good absorber of radiation at a given wavelength. Reason : According to Kirchoff's law the absorptivity of a body is equal to its emissivity at a given wavelength.

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

A. If both assertion and reason are true and reason is the correct explanation of assertion

Step-by-step solution

According to Kirchhoff's law, a=e . or the absorptivity of a body equals its emissivity. A good absorber is a good emitter. As a good absorber is poor reflector, emitting (or radiating) ability of body is oppositely related to its ability to reflect. Therefore good emitter (or radiator) is a poor reflector.

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