A body is in thermal equilibrium with its surroundings

PHYSICS · Single correct · CBSE · Physics · Thermal Properties of Matter · Thermal Properties of Matter

Problem

A body is in thermal equilibrium with its surroundings. Which relation between its absorptive power

a_{\lambda}

and emissivity

\varepsilon_{\lambda}

at a given wavelength

\lambda

is valid? (a)

a_{\lambda}+\varepsilon_{\lambda}=1

(b)

a_{\lambda}=\varepsilon_{\lambda}

(c)

a_{\lambda}\,\varepsilon_{\lambda}=1

(d)

a_{\lambda}>\varepsilon_{\lambda}\;\text{for all }\lambda