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Physics · PYQ NEET UG 2017
हिन्दीA spherical black body with a radius of \( 12\text{ cm} \) radiates \( 450\text{ watt} \) power at \( 500\text{ K} \). If the radius were halved and the temperature doubled, the power radiated in watt would be:
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Correct answer · Option D
\( 1800 \)
Explanation
By Stefan-Boltzmann law, \( P = \sigma A T^4 = \sigma (4\pi r^2) T^4 \). Thus \( P \propto r^2 T^4 \). \( P_2 = P_1 \times (\frac{r_2}{r_1})^2 \times (\frac{T_2}{T_1})^4 = 450 \times (\frac{1}{2})^2 \times (2)^4 = 450 \times \frac{1}{4} \times 16 = 1800\text{ W} \).
