Question

At a particular temperature and wavelength, the spectral emissive power and monochromatic absorptive power of a body are $10$ and $8$ units respectively. The emissive power of a black body at the same temperature will be :

• A. $1$ unit
• B. $1.25$ unit
• C. zero
• D. Infinity

Answer 1

Answer: (B)

$1.25$ unit

According to Kirchoff's law.
$\frac{e_{\lambda }}{a_{\lambda }}=E_{\lambda }$
Here, we are given that $e_{\lambda }$ = 10 and $a_{\lambda }$ = 8
So, $E_{\lambda }$ $=\frac{10}{8}$ $=1.25$