The emissive power of a black body at `T=300K` is `100Watt//m^(2)` consider a body B of area `A=10m^(2)` coefficient of reflectivity `r=0.3` and coefficient of transmission `t=0.5` its temperature is 300 K. then which of the followin is correct:

Options

A. the emissive power of B is `20W//m^(2)`
B. the emissive power of B is `200W//m^(2)`
C. the power emitted by B is 200 Watts
D. the emissivity of B is 0.2

Answer

B

Explanation

Since, `e=a=0.2`
Since `a=(1-r-t)=0.2` for the body B
Thus emissive power of B is given by,
`E=a E_(b)=(100)(0.2)=20W//m^(2)`