Refractive Index This is a measure of how much light

slows down when it goes into a new medium.

Symbol n n (vacuum) = 1

n (medium) = c (speed of light in vacuum)v (speed of light in medium)

Examples of refractive index:

Try these:

Snell’s Law When a light ray travels into a denser medium, it slows

down and bends towards the nornal. When it moves into a less dense medium, it speeds up and bends away from the normal.

Snell’s Law

Try these:

Careful – this time, the ray travels from water into amber, so n1 is not 1, it is 1.33.

The Critical angle

When a ray comes out of glass into air, it will bend away from the normal. The critical angle is the angle it hits the glass edge to refract exactly at 90 degrees.

It is different for different mediums

n1

n2

Total Internal Reflection

Optical fibers

The light ray is reflected all the way along the fiber by total internal reflection

Critical Angle:1.46

1.48