Step-by-step explanation:
a. Spectral Emissive power -
Spectral emissive power is the radiating emissive power about a partiular wavelength , is called the spectral emissive power .
b. Direct irradiation -
Direct irradiation is defined as the radiation travelling along a straight line from the Sun , down to the surface of the Earth .
c. Total Radiosity -
Total radiosity is defined as a radiant energy leaving a surface per unit time .
d. Diffuse Surfaces -
A diffuse surface is one where each part on the surface is at different levels and , after reflection , from the diffuse surface , the light ray are not parallel to each other but are at different angle .