Explain total internal reflection. What are its conditions?

Explanation

Total internal reflection: The phenomenon by which light is reflected back into the same medium, when lilght going from denser to rarer medium falls on the surface at an angle greater than critical angle is known as total internal reflection.
Necessary conditions for total internal reflection:
Relation between refraction index and critical angle:
using Snell.s law we have
`""^(2)mu_(1)=(sini)/(sinr)`..........1
When i=c (Critical angle)
Then `r=90^(@)`
Also `""^(2)mu_(1)=1/(""^(1)mu_(2))`
So from eqn 1 we have
`1/(""^(1)mu_(2))=(sinC)/(sin90^(@))`
`""^(1)mu_(2)=1/(sinC)`
which is the required between refractive index and critical angle.