Question

Calculate the rate at which a black body at temperature 300 degrees Celsius emits radiant energy. The black body is a sphere of diameter 20cm

Answer 1

According to the Stefan-Bolzmann law,

$L= 4\pi R^2 \sigma T^4 = 4\pi \cdot (0.1)^2 \cdot 5.67\cdot10^{-8}\cdot (273+300)^4 \approx 768\,\mathrm{W}.$