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Discussion :: Heat and Mass Transfer

  1. Which of the following statement is correct?

  2. A.

     A grey body is one which absorbs all radiations incident on it.

    B.

     At thermal equilibrium, the emissivity and absorptivity are same.

    C.

     The energy absorbed by a body to the total energy falling on it, is called emissivity.

    D.

     A perfect body is one which is black in colour.

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    Answer : Option B

    Explanation :


    A blackbody allows all incident radiation to pass into it (no reflected energy) and internally absorbs all the incident radiation (no energy transmitted through the body).
    Absorptive power is a measure of heat absorbed by an object. When heat is incident on the surface an object, a part of it is absorbed and the remaining part is reflected. Usually the absorbed radiation is converted to thermal energy, increasing the object's temperature.


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