Explain total internal reflection. What are its conditions?

Total inrternal reflection tkes place

What is total internal reflection, state the necessary conditions for it ? Find a relation between refractive index and critical angle.

What is total internal reflection of light ? What are the two essential conditions for total internal reflection to take place ?

What is total internal reflection of light ? What are essential conditions of it ? Explain the formation of mirage using this phenomena.

Explain nuclear fusion. What are the conditions for fusion?