Definitions for "Total internal reflection"
Keywords:  refract, clad, tir, incident, critical
The phenomenon by which light traveling from a high to a low material will reflect from the optical interface if the incident angle is greater than the critical angle.
When the angle of incidence of light striking the boundary surface of a substance exceeds the critical angle, the result is total internal reflection.
The phenomenon in which light is trapped (totally internally reflected) in one medium, because the refracted ray cannot exist (mathematically, according to Snell's Law, the sine function becomes greater than 1.0). Occurs when light traveling from a denser medium to a rarer medium strikes the interface at an angle of incidence greater than the critical angle for that interface. When this condition is met, light cannot be transmitted through the interface and so is all reflected back into the original material. The image to the left shows TIR just starting to occur, as the angle of incidence equals the critical angle. The critical angle and total internal reflection are covered on this page (and the next one) of this module. Not to be confused with total reflection.