Question

Rate of radiation by a black body is ‘R’ at temperature ‘T’. Another body has same area but emissivity is 0.1 and temperature is ‘2T’. Its rate of radiation is ______.

Options

• R

• (0.8) R

• (1.2) R

• (1.6) R

Answer 1

Rate of radiation by a black body is ‘R’ at temperature ‘T’. Another body has same area but emissivity is 0.1 and temperature is ‘2T’. Its rate of radiation is (1.6) R.

Explanation:

Rate of radiation of a black body:

R = σAT⁴    ...(i)

Rate of radiation of an ordinary body:

Now, e = 0.1

T₁ = 2T

∴ R₁ = (0.1) σA(2T)⁴

= (0.1) σA(16T⁴)

= 1.6 σAT⁴

= 1.6 R ...[From (i)]