transmittance; permeability
Technical term used in physics, optics, and materials science to describe the fraction of light, radiation, or a substance that passes through a medium.
The transmittance of this glass is over 90%.
Measure the permeability of the film.
Reflectance; the fraction of incident light or radiation that is reflected, as opposed to transmitted.
moisture vapor transmission rate; MVTR
Compound of 透過 (transmission, penetration) and 率 (rate, coefficient).