Linked from
The 16 pages that link to Transmittance, each with the reason it gives.
ReflectanceRelated: It distinguishes light passing through a sample from light reflected by it.
IrradianceRelated: Some irradiance passes through a surface rather than being absorbed or reflected.
AbsorbanceRelated: Absorbance is calculated as the negative base-10 logarithm of transmittance.
Absorption (electromagnetic radiation)Related: A decrease in transmittance can signal absorption.
Optical filterRelated: A filter's transmission spectrum quantifies which wavelengths it passes.
One-way mirrorRelated: The view through the pane depends on its transmitted light.