3. Transmit and Absorb. What is the relationship between the transmission of light and absorption of light?

Transmission is the passage of electromagnetic radiation through a medium. Both processes can be accompanied by diffusion (also called scattering), which is the process of deflecting a unidirectional beam into many directions. In this case, we speak about diffuse reflection and diffuse transmission. When no diffusion occurs, reflection or transmission of an unidirectional beam results in an unidirectional beam according to the laws of geometrical optics. In this case, we speak about regular reflection (or specular reflection) and regular transmission (or direct transmission). Reflection, transmission and scattering leave the frequency of the radiation unchanged. Exception: The Doppler effect causes a change in frequency when the reflecting material or surface is in motion. Absorption is the transformation of radiant power to another type of energy, usually heat, by interaction with matter. The absorptance α of a medium is defined by the ratio of absorbed radiant power to incident radiant power. Being ratios of radiant power values, reflectance, transmittance and absorptance are dimensionless. Quantities such as reflectance and transmittance are used to describe the optical properties of materials. The quantities can apply to complex radiation or monochromatic radiation. The optical properties of materials are not a constant since they are dependent on many parameters such as:

thickness of the sample

surface conditions

angle of incidence

temperature

the spectral composition of the radiation (CIE standard illuminants A, B, C, D65 and other illuminants D)

polarization effects