4.2 Properties of Visible Light Grade Eight Science Discovering Science 8

Wave Model of Light The wave model of light states that light is a type of wave that travels through empty space and transfers energy from one place to another. The light we see is a wave that our eye can detect. It is called visible light. Visible light is made up of several different wavelengths of light. Together they are called the visible spectrum.

The Visible Spectrum The visible spectrum is a range of colours that the human eye can detect. They fall into a range that covers seven broad categories. The visible spectrum includes the following colours: RED, ORANGE, YELLOW, GREEN, BLUE, INDIGO, VIOLET

The Visible Spectrum Sometimes these colours are abbreviated to read: R O Y G B I V This looks like a person’s name and is easy to remember. Listen to this song to help you remember!!!

The Visible Spectrum Red light has the longest wave length (700 nm) and they get shorter as you move through the spectrum. Violet light has the shortest wave length (400 nm).

Refraction The light we see is called white light. It is made up of all of the different colours of light, each having different wavelengths and frequencies. When white light travels from one material to another, each colour of light slows down and changes direction a bit differently. This “bending” of light is called refraction. Because each colour refracts a little differently we are able to see all the different colours.

Refraction As white light passes through the prism, each colour refracts differently and we are able to see the colours which make up the visible spectrum.

Isaac Newton and the Visible Spectrum Isaac Newton was one of the of the first people to prove that white light contained different colours. He passed light through a prism and was able to produce a little rainbow, which was the visible spectrum. To prove that the colours were in the light and not the prism itself, Newton passed the coloured light through a second prism and he was able to recombine the colours to produce white light.

How do we see different colours? When white light strikes an object, some of that light bounces off. This is called reflection. The colours that we see are the colours that are being reflected. The other colours are all being absorbed by the object.

Colours We can use red, green and blue to make all the colours of the rainbow. They are called additive primary colours because they can all be added together to produce white light.