Refraction

 Refraction is a bend in the ray. Light bends when it moves from one substance to another. When a ray heads toward the normal, (the line perpendicular to the plane), once it hits the normal it bends. For example when light shines through air and then to the glass light is refracted. Air is less dense then glass so it would go through air a lot faster then it does glass. Glass is denser causing them to slow down so the wave is bended. Another example is a cup filled with water and a pencil is placed into the cup. The pencil will look like it is bending. (See the picture on the right) The pencil refracts in water. Refraction accrues with water and substances such as glass. When something is refracted it has an angle of incidence and an angle of refraction but they are not equal. The ray that head towards the normal forms the incidence angle and once the ray hits the normal it comes out and form the angle of refraction.
There is a connection between the angle of incidence and the angle of refraction, this is called the law of Snellius, the formula is sin(i)/sin(r) = n. Where 'i' is the angle of incidence, 'r' the angle of refraction and 'n' a material constant. Some of these constants are in the table below.

Materialn
Alcohol1.362
Diamond2.417
Glass1.51
Water1.333

You can see a ray of light refracting in the applet on the right.

Not all colors refract equally, red refracts the less, and blue refracts the most. This is the most visible when you send a white beam of light through a prism, you can see a "rainbow" of colors coming out of it. The illustration below previews this effect.

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