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Refraction of Light

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Refraction of Light

Aim:

To find a relationship between the angles of incidence and the angles

of refraction by obtaining a set of readings for the angles of

incidence and refraction as a light ray passes from air into perspex.

Introduction:

Refraction is the bending of a wave when it enters a medium where it's

speed is different. The refraction of light when it passes from a fast

medium to a slow medium bends the light ray toward the normal to the

boundary between the two media. The amount of bending depends on the

indices of refraction of the two media and is described quantitatively

by Snell's Law. (Refer to diagram below)

The index of refraction is defined as the speed of light in vacuum

divided by the speed of light in the medium. In this experiment, the

index of refraction for the perspex is 1.50.

Snell's Law relates the indices of refraction of the two media to the

directions of propagation in terms of the angles to the normal. It

refers to the relationship between the different angles of light as it

passes from one transparent medium to another. When light passes from

one transparent medium to another, it bends according to Snell's law

which states:

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where:

n1 is the refractive index of the medium the light is leaving,

n2 is the refractive index of the medium the light is entering,

sin 2 is the is the incident angle between the light ray and the

normal to the medium to medium interface, sin 1 is the refractive

angle between the light ray and the normal to the medium to medium

interface.

Definitions:

Angle of incidence: The angle made between an incident ray and the

normal to the surface that it strikes.

Angle of refraction: The angle made between the reflected ray and the

normal to the surface that it strikes.

Medium: The substance carrying a mechanical wave.

Refraction: The bending of the direction of travel of light as it
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