If emissivity of bodies X and Y are e\_x and e\_y and absorp... | Physics - Heat Transfer (Thermal Radiation) | SolveeIt | Solveeit

Today, November 14

Question

If emissivity of bodies X and Y are $e_x$ and $e_y$ and absorptive power are $A_x$ and $A_y$ then

Visual representation for Physics

A

$e_y > e_x$ ; $A_y > A_x$

B

$e_y < e_x$ ; $A_y < A_x$

C

$e_y > e_x$ ; $A_y < A_x$

D

$e_y = e_x$ ; $A_y = A_x$

Answer

$e_y > e_x$ ; $A_y > A_x$

Explanation

Solution

The graph shows that body Y cools down faster than body X. The rate of cooling is directly proportional to emissivity. Thus, $e_y > e_x$ . According to Kirchhoff's Law of thermal radiation, emissivity equals absorptive power ( $e=A$ ). Therefore, $A_y > A_x$ .