Question

Two bodies of same shape and having emissivities 0.1 and 0.9 respectively radiate same energy per second. The ratio of their temperature is :

• A. $\sqrt{3}:1$
• B. $1:\sqrt{3}$
• C. $3:1$
• D. $1:3$

Answer 1

Answer: (A)

$\sqrt{3}:1$

$\frac{E}{t}=e\sigma A{T}^4$

From above equation which is Stefan's Law of radiation, it is clear that:
$\frac{E_1}{E_2}=\frac{e_1\sigma T_1^4}{e_2\sigma T_2^4}$

$1=\frac{0.1T_1^4}{0.9T_2^4}$

$\frac{T_1}{T_2}=\frac{\sqrt{3}}{1}$