Solar constant, `I_(s)` is defined as intensity of solar radiation incident on the Earth. Its value is close to `1.4 kW//m^(2)`. Nearly `68%` of this energy is absorbed by the Earth. The average temperature of Earth is about 290 K. Radius of the Earth is `R_(e) = 6000 km` and that of the Sun is `R_(s) = 700,000 km`. Earth - Sun distance is `r = 1.5 xx 10_(8) km`. Assume Sun to be a black body.
(a) Estimate the effective emissivity of earth.
(b) Find the power of the sun.
(c) Estimate the surface temperature of the Sun.

Answer

(a) `0.6` (b) `3.96xx10^(26)` (c) 5800 K