The value of the total radiant energy flux density at the Earth from the sun normal to the incident rays is called the solar constant of the earth. The observed value integrated over all emission wavelengths and referred to the mean Earth-Sun distance is:

Solar constant = 0.136Js -1cm-2

(a) Show that the total rate of energy generation of the sun is 4 × 1026 Js-1
(b) From this result and the Stefan-Boltzmann constant σB = 5.67 × 10–12 Js-1 cm-2 K-4,
Show that the effective temperature of the surface of the sum treated as a black body is T ( 6000K. Take the distance of the Earth from the sun as 1.5 × 1015 cm, and the radius of the sun as 7 × 1010 cm,