Question

The temperature of a body is increased from ${-73}^{0}C$ to ${327}^{0}C$. Then the ratio of emissive power is

• A. $1/9$
• B. $1/27$
• C. $27$
• D. $81$

Answer 1

The correct option is D $81$

Emissive power E is directly proportional to temperature T.

So, $E\propto T^4$

Also $T_1=-{73}^{0}C=200K$

$T_2={327}^{0}C=600K$

Thus,

$\frac{E_1}{E_2}=\frac{T_1^4}{T_2^4}$

i.e. $\frac{E_1}{E_2}=\frac{{200}^4}{{600}^4}$

i.e. $\frac{E_1}{E_2}=\frac{1}{81}$

Thus ratio of emissive power will be 81. Thus correct option is D.