Question

What are natural phenomenon where refraction occurs?

Answer 1

1. Twinkling of stars

2. Advance sunrise

3. Delayed sunset

Hope it helps.......

Answer 2

Refraction i.e. a phenomenon which occurs when waves of light passes from one transparent medium to another and thus bending at boundary between the two mediums on account of changes in the speed of lightwaves.  

Naturally occurring example of refraction is a rainbow which is created when sunlight is refracted by rain dropslets in the clear sky.