The process of bending of light ray, which is travelling from one medium to another medium.
Light ray passing from one medium (air) to another medium bends and travels.
Example: Pencil immersed in water appears as if it was bent. When you take out the pencil from the water you will not observe any bends.
The light ray coming from the object bends and comes to form an image in our eye, hence will look as if it was bent.
We are able to see the different objects because the light coming from the object forms an image in our eye. As light ray travels in straight line, we will observe all the objects without any deviation.
The light coming from the tip of the pencil starts in water and then moves in air, then reaches our eye.
As the light rays come out from water to air they are refracted (bent).
Light travels with different speeds in different mediums.
Light travels much faster in rarer medium (less dense medium -- example: Air).
Light travels with less speed in denser medium (example � water).
Due to this change in speed light bends and travels when passing from one medium to other medium.
When the light ray passes from rarer medium to denser medium it bends towards the normal.
Example: Light ray passing from air to glass (Air � rarer medium, Glass - denser medium.
When the light ray passes from denser medium to rarer medium it bends away from the normal
Example: Light ray passing from Glass to Air (Air - rarer medium, Glass - denser medium.)
Related Terms: Reflection | Total Internal reflection | Critical Angle.