Stefan Boltzmann Law - Practice Questions & MCQ

• According to Stefan Boltzmann law, the radiant energy emitted by a perfectly black body per unit area per sec is directly proportional to the fourth power of its absolute temperature,

       or emissive power of the black body is directly proportional to the fourth power of its absolute temperature ().

     i.e  

where 

Stefan's constant

and its value is

• For ordinary body

            1.  Emissive power is  given by  

           So according to Stefan Boltzmann law

where   = represent emissivity of the material

2. Radiant energy-

If Q is the total energy radiated by the ordinary body then

3. Radiant power (P): It is defined as the energy radiated per unit area.

i.e   

4.  If an ordinary body at temperature  is surrounded by a body at a temperature  

                    Then according to Stefan Boltzmann law