Assuming the sun to be a spherical body of radius $\mathrm{R}$ at a temperature of $\mathrm{T} \mathrm{K}$, evaluate the total radiant power, incident on Earth, at a distance $r$ from the Sun.

• A

  $\frac{\mathrm{R}^2 \sigma \mathrm{T}^4}{\mathrm{r}^2}$
• B

  $\frac{4 \pi r_0^2 R^2 \sigma T^4}{r^2}$
• Correct answer
  C

  $\frac{\pi r_0^2 R^2 \sigma T^4}{r^2}$
• D

  $\frac{r_0^2 R^2 \sigma T^4}{4 \pi r^2}$

Hence, the correct answer is option: 'C'.