Light Dispersion

In a rainy season, after rainfall you may have enjoyed scenic beauty in nature, which looks like bow (arc) with multiple colours, what we call it? Rainbow! Isn’t it? Hold the plastic scale/protractor (transparent) or compact disc (CD) the path of sunlight, what do you see?See the picture below, think and relate with the rainbow?

You may wondered by knowing that the light what we see and appears white is actually multicoloured light. It is combination of seven different colours!

Sir Isaac Newton used an instrument called prism through which he sent a rays of white light from one face. He observed that beam of seven colour is formed on either face. This is known as dispersion of light. Exactly as shown in fig .below.

The phenomenon of splitting of white light in to its component colours (seven colours) is called as dispersion of light.

The sequential pattern of colours obtained at the output is called as dispersion spectrum. Dispersion pattern consist of following seven colours in sequential manner

  1. Red: First deviated band which acts as one of the extreme colour.
  2. Orange
  3. Yellow: It is acts as mean colour of dispersion spectrum.
  4. Green
  5. Blue: It scatters most in the atmosphere, hence sky appears blue.
  6. Indigo.
  7. Violet: Second extreme colour.

The sequential pattern of colours can be kept in a mind by keeping the memorising the following name.

‘ROY G. BIV’

If we arrange the dispersion spectrum according to the decreasing order of its wavelength, then can be read as

‘VIBGYOR’

Alternately what will happen if you combine all the seven colours listed above? You will that combination of these colours gives rise to white light.

Q. Define dispersion of light.

Ans:The phenomenon of splitting of white light in to its component colours (seven colours) is called as dispersion of light.

Q. Who studied dispersion using prism?

Ans: Sir Isaac Newton

Q. What do you mean by dispersion spectrum?

Ans: The sequential pattern of colour obtained after separation of white light into seven colours is called as dispersion of light.

Q. List the colours in dispersion pattern.

Ans: Red, Orange, Yellow, Green, Blue, Indigo and Violet.

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