Hello

Total internal reflection is the complete reflection of a light ray reaching an interface with a less dense medium when the angle of incidence exceeds the critical angle.

The conditions to have total internal reflection are given below:-

• The light should be travelling from an optically denser medium i.e higher refractive index to an optically less dense medium i.e lower refractive index
• the angle of incidence should be greater than the critical angle.

I hope that it helps you

Thankyou