TIR (Total Internal Reflection) Optic
When light passes from a high refractive-index medium (such as glass) to a low refractive-index medium (such as air) there is a special angle, known as the critical angle, above which light is 100% reflected. Any light rays that fall within the critical-angle undergo total internal reflection. Carclo TIR optics use this principle to produce highly efficient optics with a huge variety of beam shapes.
This is a term used for LED’s to describe the range of their angular output. It is the total cone angle in degrees at which the off-axis intensity falls to 50% of the on-axis peak.
Distance between two points of corresponding phase and is equal to waveform velocity divided by frequency.