6 critical angle tir, emr, colour addition (8.3)

6 Critical Angle TIR, EMR

8.3 Critical Angle TIR, EMR, Colour addition

TIRSince the transmitted light enters a less optically dense medium it travels faster and is refracted away from the normal.

As the angle of incidence is increased, the angle of refraction also increases. This continues until, at a certain angle of incidence called the critical angle, , the angle of refraction will be almost 90° and the transmitted ray travels just along the surface of the water.

When a light ray exceeds the critical angle it undergoes total internal reflection (TIR).

Optical fibers are widely used in fiber-optic communications, where they permit transmission over longer distances and at higher bandwidths (data rates) than wire cables. Fibers are used instead of metal wires because signals travel along them with less loss and are also immune to electromagnetic interference.

How to calculate

Note: It only exists when you have the light going from a medium with a higher refractive into a medium with a lower refractive index.

electromagnetic radiation (EMR)

Read page 274 of your text book for a description of Electromagnetic Radiation.

EMR Categories

Coloured light, different wavelengths

Why is the car green?

• A green object is using the light from the sun to show it’s colour. The suns light is white, so made up of all colours of light.

• A green car absorbs all colours of light other than green. The green is reflected and is taken in by our eyes.

The green car

Coloured filters

• Coloured filters have the same effect as coloured objects. The difference is, rather than reflected the extra light, they let it pass through.

• They absorb all colours of light except theirs.• Eg: A red filter absorbs all colours except red and only allows red to be transmitted.

Colour addition or mixing light sources

Summary