1 Total internal reflection is the phenomenon which occurs when a propagated wave strikes a medium boundary at an angle larger than a particular critical angle with respect to the normal to the surface.

2 It refers to the complete reflection of a ray of light within a given medium from the surrounding surface. here, the ray of light continues to be reflected within the medium(glass,water,etc) without being refracted.

3 when a ray of light is passing from a denser medium to rarer medium , if we increase the angle of incidence with normal then at an angle known as critical angle a particular condition arrives in which the refracted ray becomes parallel to the boundary surface.

4 If any ray of light moving from denser medium to rarer medium strikes the boundary surface having incident angle greater than critical angle, then the ray of light continues to be reflected within the medium being refracted.

This is known as total internal reflection(TIR)

• Total internal reflection:

  When the incident angle $Φ_1$ is higher than critical incident angle $Φ_c$ the whole path of the light is reflected back in the first medium. This is known as Total Internal Reflection (TIR).

$$Φ_1\gtΦ_c …………. Condition \ \ \ for \ \ \ TIR$$