Physics:Light guide

Transparent material to guide a flow of light by the use of total reflection.

Typical materials are:

• - plexiglass, plastic, glass;
• - fibre light guides (consisting of a number of thin light guide fibres);
• - liquid light guides.

Due to Liouville's law, the total area of the cross-section along a light guide cannot be reduced without light losses. For changes in direction a maximum bending (minimal bending radius) should be chosen according to the relation

where

With a radius chosen according to the relation given above, all light entering the plane front surface of a light guide is transported due to total reflection.

Losses are due to absorption ( light attenuation) and imperfect surfaces. Absorption and total reflection angle depend on the wavelength.