If 150 J of energy is incident on area ` 2m^(2)` . If `Q_(r)=15J`, coefficient of absorption is 0.6 , then amount of energy transmitted is

Options

A. 50 J
B. 45 J
C. 40 J
D. 30 J

Answer

B

Explanation

When thermal radiations (Q) fall on a body , they are partly reflected, partly absorbed and partly transmitted.
` Q=Q_(a)+Q_(r)+Q_(t)`
and ` (Q_(a))/(Q)+(Q_(r))/(Q)+(Q_(t))/(Q)=a+r+t=1 `
`implies (15)/(150)+0.6+x=1`
or `0.1+0.6+x=1`
or x=0.3
Transmitting power , ` t=(Qt)/(Q)`
`or 0.3=(Q_(t))/(150)`
`implies 45J`