b
(b) Kirchhoff's law states that, the ratio of emissive power to the absorptive power corresponding to a particular wavelength and at a given temperature is constant for all bodies\(:\)

\(e_{\lambda} / a_{\lambda}=\) constant \(=E_{\lambda}\)

where \(E_{\lambda}=\) emissive power of a perfect black body corresponding to same wavelength and temperature, it is clear from above relation that if \(a_{\lambda}\) (absorptive power) is large for a body, \(e_{\lambda}\) (emissivetive power) will also be large to keep the ratio constant i.e. good absorbers are good emitters.