If between wavelength $\lambda $and $\lambda + d\lambda $, ${e_\lambda }$and ${a_\lambda }$ be the emissive and absorptive powers of a body and ${E_\lambda }$ be the emissive power of a perfectly black body, then according to Kirchoff's law, which is true
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(c)According to Kirchoff’s law, the ratio of emissive power to absorptive power is same for all bodies is equal to the emissive power of a perfectly black body i.e.,
${\left( {\frac{e}{a}} \right)_{body}} = {E_{{\rm{Black}}\,{\rm{body}}}}$ for a particular wave length
${\left( {\frac{{{e_\lambda }}}{{{a_\lambda }}}} \right)_{{\rm{body}}}} = {({E_\lambda })_{{\rm{Black}}\,{\rm{body}}}}$ ==> ${e_\lambda } = {a_\lambda }{E_\lambda }$
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