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MHT CET 2026 (13 May, Shift 2) · Thermal Radiation: Black Body, Stefan & Wien

Thermal Radiation: Black Body, Stefan & Wien question from MHT CET 2026 (13 May, Shift 2)

Q18MHT CET 2026 · 13 MAY · SHIFT 2Medium

Thermal Radiation: Black Body, Stefan & Wien

The radiation emitted by a star A is $10000$ times that of the sun. If surface temperature of sun and star A are $6000$ K and $2000$ K respectively, the ratio of radii of star A and sun is

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Answer: (b)

Power of a star $P = 4\pi r^2 \sigma T^4$ , so $P \propto r^2 T^4$ .
$\dfrac{P_A}{P_S} = \left(\dfrac{r_A}{r_S}\right)^2 \left(\dfrac{2000}{6000}\right)^4 = 10000$
$\left(\dfrac{r_A}{r_S}\right)^2 = 10000 \times 81 \Rightarrow \dfrac{r_A}{r_S} = 900$
So the answer is (b) $900 : 1$ .

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