Splitting Light -
Dispersion
When white light falls obliquely on a medium
such as a glass prism or a sphere of plastic, it is refracted, or bent, and separated
into its colored components; this phenomenon is called dispersion.
This process can thus be used to split up light into its component colours. By means of a
prism, this can be done too.
It is done by just mere passing light through
a prism at an angle. The spectrum upon entering, refracts and the colours will surface
when the light rays move out of the prism. The components are thus separated.
The theory behind dispersion lies in the
varying speed of the colours in different media. Red light moves more rapidly than blue in
all media. As a result, the red light is bent less than the blue light, and other colors
fall in between. After passing through the medium, white light is dispersed into its
components.
How to recombine the
colours
back into a light ray
If you want to recombine
the colours, there are also solutions.
(1) Place another prism near the first prism
and when the colours enter the second, they are recombiend into one again.
(2) Use a converging lens. Place the
converging lens just somewhere near the prism. When the colours enter the lens, they are
converged into one again - the visible spectrum , light.
The diagrams below illustrate all the
processes of dispersion and recombination.
Although dispersion has long been observed in
nature, Sir Isaac Newton was the first scientist to discover that visible light consists
of 7 colours and the methods to split and combine them. He was also the first person
to use a second prism to recombine the colours into light again, proving that the mixture
is just light.
