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Questions
How does the deviation produced by a triangular prism depend on the colour (or wavelength) of light incident on it?
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Solution 1
Light of different colours have different speeds in a medium.
Therefore, the refractive index of glass (the material of prism) is different for different colours of light and the deviation caused by a prism is different for different colours of light.
Violet is deviated the most because in glass, speed of violet is least.
Red is deviated the least because in glass, speed of red is most.
Solution 2
Because different colours have different wavelengths in the medium, the deviation that a prism produces depends on the colour (or wavelengths) of the light that impinges on it. Consequently, for various colours of light, the refractive index of glass (the prism's substance) differs, and the deviation brought about by the prism varies accordingly.
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