What is the physical meaning of emissivity?write it’s unit
In the MKS unit system, radiative flux is given in joules per second (watts) per square meter (W/m²).
Emissivity () is the ratio of a surface’s ability to emit radiant energy compared with the ability of a perfect black body of the same area at the same temperature. Emissivity is a dimensionless constant having values between 0 and 1. Perfect reflectors would have Emissivity = 0. Perfect absorbers would have Emissivity = 1.