Colours of Light by 2E1 Marcus Choo

Colour :
I have learnt that white light, ( ordinary light ), is a mixture of different colours. When a beam of white light passes through a glass prism, the light splits into seven different colours : Red, Orange, Yellow, Green, Blue, Indigo, Violet. We can get white light back again by combining the colours back together. By using a second prism, or by spinning a colour wheel.

We can see the colours of the spectrum, so it is called the visible spectrum. Some people think the there are only six colours as indigo cannot be easily distinguished from blue and violet.

There are three sections : primary colours, secondary colours and teitary colour. Primary colours consist of : Red, Blue and Green.
Secondary colours consist of : Yellow, Cyan and Magenta.
While teitary colour consist of only : White.

A colour filter is a clear plastic or glass that only lets some colours pass through and absorbs the others.

When white light shines on a colours object, some of the colours in the spectrum are reflected and some are absorbed. We see the colour of the reflected light. The colour of an object is the colour of the light that is reflected from it into our eyes.

When the eye detects light, an image is formed on the retina, ( the back of the eye ). The retina has two kinds of light sensitive cells, they are called the rods and the cones. These cells are connected to a nerve which carries signals to the brain, the brain than interprets the signals as light. The rods do not detect colour, they are sensitive to black and white, and work best in dim light. The cones however, detect colour and work best in bright light.

There are tree types of cone cells, one detects red light, another detects blue light and the other detects green light. This means that these cone cells can detect the three primary colours. When white light shines into the eye, all three types of cones respond. For example the cones which detect red light respond to the red light in the white light and the brain receives signals from all these types of cones and interprets them as white light.