Refraction of Light by 2E1 Fatima

What is refraction?
Refraction is the bending of a light when it passes from one transparent medium into another.

When and how does it happen?
Light changes direction because light travels at different speeds in different substances, causing it to be bent when it changes from one substance to another.

The degree of refraction depends in part on the angle at which the light hits the surface of a material. A line perpendicular to that surface is called the normal. The angle between the incoming light ray and the normal to the surface is called the angle of incidence. The angle between the refracted ray and the normal is called the angle of refraction. The angle of refraction cannot exceed 90°.
A ray of light refracts or deviates from its original path as it passes from one optical medium to another because the speed of light changes.

Refractive Index?
The amount of refraction can be found using the refractive index.
The speed at which light travels may change as it passes from one medium to another. Different substances will cause different changes to the speed of light. For example, glass slows light more than water.

To find the effect of a substance we can calculate its refractive index. This is a ratio of the speed of light in air or vacuum and the speed of light in the substance.

refractive index = speed of light in air/speed of light in substance

For example, the speed of light in air is 300,000 km/s and in glass it travels at about 200,000 km/s. Its refractive index is therefore 1.5. Water, however, has a refractive index of 1.33. This means that light rays are refracted more when they enter glass than when they enter water.

Effects of Refraction?
The effects of refraction:
1. Make things appear to be nearer
2. make objects in water appear to be bent
the pencil appears to be bent because of refraction

DK Reference Encyclopedia
http://www.tutorvista.com/content/physics/physics-ii/light-refraction/refraction-light.php
http://images.google.com.sg/