CBSE Class 10 Science 2019 · Paper 31/2/3 · Question 6(a)
What happens to a beam of white light when it gets refracted through a glass prism ? Which colour deviates the most and the least after refraction through a prism ? What is likely to happen if a second identical prism is placed in an inverted position with respect to the first prism ? Justify your answer.
Answer
White light disperses into seven colours, violet deviating most and red least; an inverted identical prism recombines them into white light.
White light splits into its seven component colours (violet, indigo, blue, green, yellow, orange, red), forming a spectrum; this is called dispersion, and it happens because glass bends each colour through a different angle. Violet deviates the most and red the least.
If a second identical prism is placed in an inverted position, the colours recombine and white light emerges from the second prism. Justification: the inverted prism deviates each colour through the same angle as the first prism but in the opposite direction, so all the colours come together again (Newton's experiment), showing that white light is made up of these seven colours.
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