Total Internal Reflection
Total Internal Reflection (TIR) refers to the complete reflection of light rays within an optically denser medium.
Critical angle, c, is the angle of incidence in the optically denser medium for which the angle of refraction in the less dense medium is 90⁰.
To calculate critical angle, use this formula:
Two conditions for it to take place:
Note that if first condition is not satisfied, we can forget about second condition because when light travels from an optically less dense medium to a denser medium, the light ray bends towards the normal.
To help you understand Total Internal Reflection better, you can play with the applet below.
Application of TIR: Optical Fibres in telecommunication
Optical Fibres are very fine, optically pure glass fibre through which light undergoes total internal reflection to transmit data from one end to the other.