सभी वास्तविक पदार्थों के लिए, अवशोषकता (absorptivity) का मान किसके बीच होना चाहिए?

For an opaque body, the relation between absorptivity α, reflectivity ρ, and transmissivity τ is:

The physical law stating that the total energy emitted per unit surface area of a black body is directly proportional to the fourth power of its absolute temperature is: