Assuming the sun to be a spherical body of radius $\mathrm{R}$ at a temperature of $\mathrm{T} \mathrm{K}$,…

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.
  1. $\frac{\mathrm{R}^2 \sigma \mathrm{T}^4}{\mathrm{r}^2}$
  2. $\frac{4 \pi r_0^2 R^2 \sigma T^4}{r^2}$
  3. $\frac{\pi r_0^2 R^2 \sigma T^4}{r^2}$
  4. $\frac{r_0^2 R^2 \sigma T^4}{4 \pi r^2}$

Solution

$\frac{\pi r_0^2}{4 \pi r^2}\left(\sigma \mathrm{T}^4 \cdot 4 \pi \mathrm{R}^2\right)=\frac{\sigma \pi \mathrm{T}^4 \mathrm{R}^2 \mathrm{r}_0^2}{\mathrm{r}^2}$

Asked in: JEE Main 2006

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