Fri March 06, 2015 By: Raghav Dinesh

Issac Newton showed that a glass prism can cause the dispersion of white light and he also showed about how if an inverted prism is kept near the other prism The 7 colours join back to form a white light .
What if the second prism is kept upright ? What happens to the spectrum of colours ? 

Expert Reply
Jyothi Nair
Sat March 07, 2015
The coloured band obtained on a screen after passing white light through a prism is called the spectrum. Bending is least for the red colour and maximum for violet colour.
In the Newton's experiment showing recombination of light, if the  second prism is kept upright i.e same as that of the first prism then a widely seperated band of seven colours will be formed in the same order. All the colours will get refracted towards the base of the prism. On the other hand when he turned the second prism in such a way that the refracting surfaces are parallel to each other, the seperate bands formed combined to form white light again. 
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