Transmission is the outgoing phenomenon of incident light after being refracted through an object. The objects to be transmitted are transparent or translucent, such as glass, color filters, etc. If the transparent body is colorless, most of the light is transmitted through the object, except for a small amount of light that is reflected. In order to express the degree to which a transparent body transmits light, the ratio τ of the transmitted luminous flux to the incident luminous flux is usually used to characterize the light transmission property of the object, and τ is called transmissivity.
