Question

The spectral emissive power E? for a body at temperature T1 is plotted against the wavelength and area under the curve is found to be A. At a different temperature T2, the area is found to be 9A. Then ?1/?2

Answer 1

For a radioactive body the ratio of T1/T2 will be (9)^1/4.

The relation between emissive power E, temperature T and area A of a radioactive body can be determined by Stefan's law.

According to Stefan's law,

Spectral emissive power can be determined by,

E=sigma**A*T^4

Where,E=Spectral emissive power

T=temperature of the body

A=Area of the body

Sigma=Stefan's constant

For a body of constant temperature E,

T^4 will be inversely proportional to A.

Hence,

A1/A2=T1^4/T2^4

Or,9A/A=T1^4/T2^4

Or,T1/T2=(9)^1/4

Hence for the body the ratio will be (9)^1/4.