Refraction

Refraction of Light

When a beam of light strikes an optical medium (such as a transparent material), it is partially reflected off the surface and partially transmitted through the medium. The reflected light follows the law of reflection. The light that is transmitted through the medium bends as it travels from one optical medium to another. This bending effect is known as refraction.

An example would be the  optical illusion that 

the pencil is actually  bending in the  cup 

of water.

Why

Refraction occurs because of the difference in the speed of light travel in different mediums. The bending of light only occurs at the interface. Within the same medium, light still travels in a straight line. Also, the higher the optical density of a medium, the lower the transmittance, thus the greater is the refraction of light in the medium.

Although we know that a light ray will refract when it travels from one optical medium to another, but exactly how much does it bent? To calculate this, Snell's Law needs to be used.

How do you draw diagrams?

1) Mark out one point on the object.
2) Draw the corresponding point on the image. (distance of image = ¾ of distance of object)
3) Use broken lines to construct the image.
4) Draw 2 rays from one image point to the eye.
5) Draw 2 rays from the corresponding object point to the points of refracted rays at the interface.
6) Draw arrowheads to indicate the direction of light travel.