Refraction.
Refraction occurs for any waves, where there's a change in the medium.
Refraction
decreased
Yes, it is true.
The lens.
The retina.
It is because of the change in velocity of light in two different media.
No
Refraction happens in the cornea of the eye. It can be corrected with glasses or contacts.
When light reaches the lens of the eye, it bends. This change in the direction of the light is called refraction, and it is what makes the images one sees.
The word is rainbow. Rainbows occur when light is reflected inside droplets of water and then refracted out into the air.