What is "transmittance"

Transmittance \Trans*mit"tance\, n. Transmission.

1786, from transmit + -ance.

n. 1 a transmission 2 (context physics English) the fraction of incident light, or other radiation, that passes through a substance

n. the fraction of radiant energy that passes through a substance [syn: transmission]

Transmittance of the surface of a material is its effectiveness in transmitting radiant energy. It is the fraction of incident electromagnetic power that is transmitted through a sample, in contrast to the transmission coefficient, which is the ratio of the transmitted to incident electric field.

Internal transmittance refers to energy loss by absorption, whereas (total) transmittance is that due to absorption, scattering, reflection, etc.