what are the three conditions that must be met for refraction to occur

a light ray will be refracted  if the following condition occur

·       there must be two different media with different densities , otherwise  the light ray will just continue in the next medium un-refracted.

·       the incident angle must be less than 90° or must not fall at the normal.

·       and the incident angle must be greater than  the critical angle otherwise , the light ray will just be totally  reflected internally.