REFRACTION(Bending of Light)
Light slows down or speeds up when it enters and leaves another
material
Refraction• The change in direction of a wave as is
crosses the boundary between two media in which the wave travels at different speeds.
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 RefractionMaterial Index of RefractionVacuum 1.0000
Air 1.0003Ice 1.3100
Water 1.3330Ethyl Alcohol 1.3600
Plexiglas 1.5100Crown Glass 1.5200
Light Flint Glass 1.5800Dense Flint Glass 1.6600
Zircon 1.9230Diamond 2.4170
Rutile 2.9070Gallium phosphide 3.5000
Higher the index theslower the speed of light
The Critical Angle (c)
The Critical Angle is the angle where the light refracts along the boundary (sin2 = 90o).
Total Internal Reflection
Using a refraction simulation, we can see why this is impossible.
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”
• 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.
• 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)
• Rainbows
• Mirages