Thermal Properties Of Matter Ques 20
20. A black body at $227^{\circ} C$ radiates heat at the rate of $7$ $ cals / cm^{2} s$. At a temperature of $727^{\circ} C$, the rate of heat radiated in the same units will be:
[2009]
(a) $50$
(b) $112$
(c) $80$
(d) $60$
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Answer:
Correct Answer: 20.(b)
Solution:
- (b) According to Stefan’s law $E=\sigma T^{4}$,
$T_1=500 K$
$T_2=1000 K$
$\frac{E_2}{E_1}=(\frac{T_2}{T_1})^{4}=(\frac{1000}{500})^{4}=16$
$\therefore \quad E_2=16 \times 7=112$ $ cal / cm^{2} s$
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