State (i) Stefan-Boltmann law and (ii) Wein’s displacement law.

Question

State (i) Stefan-Boltzmann law and 

(ii) Wein’s displacement law.

Answer 1

(i) The Stefan-Boltzmann law : The rate of emission of radiant energy per unit area or the power radiated per unit area of a perfect blackbody is directly proportional to the fourth power of its absolute temperature. OR The quantity of radiant energy emitted by a perfect blackbody per unit time per unit surface area of the body is directly proportional to the fourth power of its absolute temperature.

(ii) Wien’s displacement law : The wavelength for which the emissive power of a blackbody is maximum, is inversely proportional to the absolute temperature of the blackbody.

OR 

For a blackbody at an absolute temperature T, the product of T and the wavelength λ_m corresponding to the maximum radiation of energy is a constant.

λ_m T = b, a constant. 

Notes: 

(1) The law stated above was stated by Wilhelm Wien (1864-1928) German Physicist. 

(2) The value of the constant b in Wien’s displacement law is 2.898 × 10^-3 m.K.