Question 362: Properties of Matter

Question

The total radiant energy per unit area, normal to the direction of incidence, received at a distance R from the centre of a star of radius r, whose outer surface radiates as a black body at a temperature TK is given by

Accepted Answer

According to the Stefan Boltzmann law, the power radiated by the star whose outer surface radiates as a black body at temperature T K is given by
$$P = \sigma 4\pi {r^2}{T^4}$$
where, r = radius of the star
$$\sigma $$ = StefanÃ¢ÂÂs constant
The radiant power per unit area received at a distance R from the centre of a star is
$$S = {P \over {4\pi {R^2}}} = {{\sigma 4\pi {r^2}{T^4}} \over {4\pi {R^2}}} = {{\sigma {r^2}{T^4}} \over {{R^2}}}$$

Answer

$${{\sigma {r^2}{T^4}} \over {{R^2}}}$$

Answer

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

Answer

$${{\sigma {r^2}{T^4}} \over {{R^4}}}$$

Answer

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

Properties of Matter

The total radiant energy per unit area, normal to the direction of incidence, received at a distance R from the centre of a star of radius r, whose outer surface radiates as a black body at a temperature TK is given by

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