In physics, transmission refers to the passage of rays (light) through a medium. The measure for permeability is transmittance: this is the ratio of the transmitted luminous flux to the incident luminous flux. Similar to reflection, transmission can also be either directional or diffuse. Translucent materials are used in lighting technology to direct light, but also to model the spectrum.
Transmitting materials in luminaires can be transparent. This applies to simple cover glasses as well as to filters which absorb specific spectral ranges but transmit the others, thus creating coloured light or lowering the UV or infrared component. Occasionally, diffusing materials – for example opal glass or opal plastics – are also used as luminaire covers to avoid the effects of glare by lowering the lamp luminance.
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The ability of materials to transmit light. The dimension of transmission is transmittance, defined as ratio of transmitted luminous flux to incident luminous flux. Transmission can be directed or diffuse.
Transmission describes how the light incident on a body is totally or partially transmitted depending on the transmission factor of the given body. The degree of diffusion of the transmitted light must also be taken into account. In the case of completely transparent materials there is no diffusion. The greater the diffusing power, the smaller the directed component of the transmitted light, up to the point where only diffuse light is produced. Transmitting materials in luminaires can be transparent. This applies to simple front glass panels or filters that absorb certain spectral regions but transmit others, thereby producing coloured light or a reduction in the UV or IR range. Occasionally diffusing materials, e.g. opal glass or opal plastics, are used for front covers in order to reduce lamp luminance and to help control glare.
