Optics+Basics+and+Colour


 * Optics Basics and Colour **

We only see what light brings to our eyes.

Light is a form of ** energy **.

Light is an ** electromagnetic wave ** which is part of the electromagnetic spectrum which includes: Each of these has a different (range) of wavelengths and frequencies.
 * Radiowaves, microwaves, infrared, visible light, ultraviolet, x-rays and gamma rays. **

Anything you can see is a ** source of light **.
 * Luminous ** sources produce their own light, e.g. the sun
 * Non-luminous ** sources only reflect light.

Light can be produced by: **Incandescence**: light produced by hot matter
 * Electric discharge ** : light produced by electricity passing through matter
 * Luminescence ** : light not produced by hot matter
 * Fluorescence ** : light produced when another energy source is present
 * Phosphoresence ** : light produced after exposure to another energy source
 * Chemiluminescence ** : light produced by a chemical reaction
 * Bioluminescence ** : light produced by living things, e.g. bacteria, fungi, fish, plants, insects
 * Triboluminescence ** : light produced by rubbing, scratching or friction

When light hits an object, it can be **absorbed, reflected or transmitted**.

White light is made of the ** visible spectrum ** (rainbow):
 * Red, orange, yellow, green, blue, indigo, violet **

The colour of an object is determined by the colour(s) of light that are **reflected and absorbed.**

All the colours of visible light can be formed using only three colours: **red, green, and blue**. This is **additive colour mixing**.

The eye has two types of cells, **rods and cones**. Rods only detect the presence or absence of light but are much more sensitive. There are three types of cones, each of which is most sensitive to a particular frequency of light - red, blue or green.

Paints and dyes work via ** subtractive colour mixing ** in which more and more colours of light are absorbed.