REFRACTION (Bending of Light) Light slows down or speeds up when it enters and leaves another material

Pencil Demo

Refraction The change in direction of a wave as is crosses the boundary between two media in which the wave travels at different speeds.

Index of Refraction

Pyrex Demo

Dispersion Dispersion is the refraction of white light into separate colours. Different colours of white light travel at different speeds (v) and have a different “n” value.

Index of Refraction Higher the index the slower the speed of light

Snell’s Law

Towards the normal Away from the normal

The Critical Angle (  c ) The Critical Angle is the angle where the light refracts along the boundary (sin  2 = 90 o ).

Total Internal Reflection Using a refraction simulation, we can see why this is impossible.refraction simulation Total Internal Reflection occurs when light cannot refract but bounces back into the more dense medium.

If n1 > n2 When light passes into a less optically dense medium, it moves away from the normal line. At a large enough incident angle, light refracts at an angle of 90 degrees... This is called the “critical angle”. This is called “Total Internal Reflection”

Total Internal Reflection & the Critical Angle

Fibre optics work by total internal reflection! Information, traveling in the form of light, is able to move around the Earth very fast using fibre optics.

Fibre Optics:

Due to total internal reflection, you will see reflections of objects in water on the water- air boundary when viewed from inside the water.

Refraction Applications Diamonds Fibre Optic Cables Binoculars and Periscopes (check out this video too)Periscopesvideo Rainbows Mirages

Mirages Explained