Question

what is refraction? what is cause and condition for refraction​

Answer 1

Answer:

it is the process in which direction of propagation of light changes at the boundary when it changes it's medium...

it is caused due to change in medium by change in medium's density or temperature , etc

Answer 2

refraction is the change in direction of a wave passing from one medium to another or from a gradual change in the medium.

refractive index or index of refraction of a material is a dimensionless number that describes how fast light travels through the material. It is defined as. where c is the speed of light in vacuum and v is the phase velocity of light in the medium.

Total internal reflection when refraction reflection at critical angle and refraction takes place called TIR