Blackbody radiation — UPSC Physics Optional IFoS 2025 Paper I

Assume the Sun to be a black body at temperature 5800\text{ K}. Use Stefan's law to calculate :

(i) The total energy emitted by the Sun per second, and

(ii) The energy reaching the top of the Earth's atmosphere. Given : \sigma = 5\cdot 672 \times 10^{-8}\text{ SI units}, Radius of the Sun = 7 \times 10^8\text{ m}, The distance of the Earth's atmosphere from the Sun = 1\cdot 5 \times 10^{11}\text{ m}.