Assertion: IBB (Ideal Black Body) is a good emitter at high temperature.

Reason: Good emitters are good absorbers and vice versa.

Assertion: Absorptive power is a dimensionless quantity and a body having low emissive power should have low absorptive power.

Reason: The ratio of emissive power to absorptive power is same for all bodies at a given temperature and is equal to the emissive power of a black body at that temperature.

Assertion: A body that is a good radiator is also a good absorber of radiation at a given wavelength.

Reason: According to Kirchhoff's law the absorptivity of a body is equal to its emissivity at a given wavelength.

Assertion: Perspiration from the human body helps in cooling the body.

Reason: A thin layer of water on the skin enhances its emissivity.

Assertion: Bodies radiate heat at all temperatures.

Reason: The rate of radiation of heat is inversely proportional to the fourth power of absolute temperature.

Assertion Blue star is at high temperature than red star.
Reason Wien's displacement law states that $T\propto \left(\frac{1}{{\lambda }_m}\right).$

Assertion: If the temperature of a star is doubled, then the rate of loss of heat from it become $16$ times.

Reason: Specific heat varies with temperature under the above condition of the star.

Assertion: The radiation from the sun's surface varies as the fourth power of its absolute temperature.

Reason: The sun is not a black body.