One might ask, how does rainbow form, or why when looking at a white light, a circle of rainbow is seen in my eyes? Well, the answer is what I bring to you in the form of: Dispersion Of Light
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It is said that white light is the combination of different colours of light. Now, white light is separated into its spectrum, it is called dispersion of light. This spectrum is of seven colours which are the colours of the rainbow we see.
Dispersion of light can be achieved by incidenting a ray of white light on triangular glass prism.
When light is incidented on that prism, It is separated to seven colours which are that of the rainbow we see馃槉馃寛.
The rainbow formed in the sky is the dispersion of light in water drops. Here, the drops takes the place of the triangular prism.
The human eye is somehow similar to the sky the sclera, aqeous humor, vitreous humor e.t.c, forms the prism and these disperse light forming a circle of rainbow which is at times not too noticeable.
The spectrum of colours of light can be recombinated that is it can be reversed to its original light (colour).
How does that work?
When 2 twin prism are kept alike, the separation is seen very clearly. But when one is kept in another way, the separation come together and for a white light.
Characteristics Of Spectrum Of Light
ROYGBIV
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Increasing Wavelength
Increasing Deviation
Increasing Refractive Index
Decreasing Frequency
Note: These characteristics occur from Red to Violet.
Newton's Colour Disc.
1669
Sir Isaac Newton produced a circle plate and divided the circumference into seven parts, having the same angle from the centre and the seven parts are of seven colours of white light formed from the dispersion of white light. When the plate is spun fast, these colours seem to be grey-white, and when it is slowed down, the seven colours appear.
Pure Spectrum Of Colours
Normally, spectrum produced are impure because the rays overlap and change as the colour is not separated.
A pure spectrum is produced using a Triangular Prism, Two Converging Lenses and a Narrow Slit of White Light.
The narrow slit is used to produce series of narrow coloured images, which minimizes the chance of overlapping colours, when rays are incidented on the converging lens which refract the ray into a parallel beam and focus it on angle 60 triangular prism. The emergent rays are then focused on another converging lens to produce parallel of different colours on the screen at its focus. This produces a spectrum which does not overlap.
And so, a very pure spectrum of colour is formed.
Black absorbs all the colours and White is the combination of all colours.
Dispersion of Light is the separation of white light into its component.