The Absorptive Power of Perfectly Black Body is
The Absorptive power of perfectly Black body is 1.
Black body is an idealized physical body that absorbs all incident electromagnetic radiation. Emissivity is the energy level of black body. Construction of black bodies with emissivity as close to one as possible remains topic of current interest.
The idea of black body originally was introduced by Gustav Kirchhoff in 1860. It is true for radiation of all wavelength and for all angles of incident.
Hence the black body is a perfect absorber for all incident radiation.