Direction for: In each of the following questions a statement of Assertion is given followed by a corresponding statement of Reason just below it. Of the statements mark the correct answer as
Assertion: A body that is a good radiator is also a good absorber of radiation at a given wavelength. Reason: According to Kirchhoffs law the absorptivity of a body is equal to its emissivity at a given wavelength.A) If both assertion and reason are true and reason is the correct explanation of assertion.
B) If both assertion and reason are true but reason is not the correct explanation of assertion.
C) If assertion is true but reason is false.
D) If both assertion and reason are false.
Correct Answer: A
Solution :
According to Kirchhoffs law, the ratio of the emissive power to the absorptive power for radiation of a given wavelength is the same for all bodies at the same temperature and is equal to the emissive power of a perfectly black body at that temperature. A. conclusion from Kirchhoffs law is that, if surface is a good absorber of a particular wavelength of radiation it is also a good emitter of that wavelength of radiation.
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