Gray body characteristics
The absorption and reflection of the gray body in the visible light band is constant at each wavelength band, that is, the object without selective absorption and reflection, such as a black object, has an absorption coefficient of 1 (reflection coefficient is 0), and a white object has a reflection coefficient of 1 ( The absorption coefficient is 0), and the reflection coefficient and absorption coefficient of gray objects are constant in each wavelength band, so they appear as black or white or gray.