Haryana PMT Haryana PMT Solved Paper-2009

  • question_answer
    41.          Good emitters are good absorbers is a statement concluded from

    A)                  Newtons law of cooling

    B)  Stefans law of radiation

    C)  Provosts theory

    D)  Kirchhoffs law

    Correct Answer: D

    Solution :

                    According to Kirchhoffs law the ratio of emissive power to absorptive power is same for all surfaces at the same temperature and is equal to the emissive power of a perfectly black body at that temperature. Hence,    \[\frac{{{e}_{1}}}{{{a}_{1}}}=\frac{{{e}_{2}}}{{{a}_{2}}}=....{{\left[ \frac{E}{A} \right]}_{perfectly\,black\,body}}\] Now, since \[{{({{E}_{\lambda }})}_{black}}\]is constant at a given temperature, this implies that good absorber is a good emitter (or radiator).


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