Two spheres of the same material have radii $1\; m$ and $4\; m$ and temperatures $4000 \;K$ and $2000 \;K$ respectively. The ratio of the energy radiated per second by the first sphere to that by the second is
AIEEE 2002, Medium
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(a) $\frac{{{Q_1}}}{{{Q_2}}} = \frac{{r_1^2T_1^4}}{{r_2^2T_2^4}}$$ = \frac{{{4^2}}}{{{1^2}}} \times {\left( {\frac{{2000}}{{4000}}} \right)^4} = 1$
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