Question

Assuming the sun to be a spherical body of radius R at a temperature of TK, evaluate the total radiant power, incident on earth, at a distance r from the sun.

where, r0is the radius of the earth and σ is Stefan'* constant.

Answer 1

Correct Option (b)

Explanation:

From Stefan'* law, the rate at which energy is radiated by sun at its surface is

P = σ x 4πR2 x T4

[sun is a perfectly ***** body as it emits radiations of all wavelengths and so for it,e =1]

The intensity of this power at earth'* surface (under the assumption r > >r0) is