What is cause of dispersion of white light and formation of spectrum??

Dear Student

Dispersion of white light is defined as splitting of white light into seven constituent colours when passed through the prism.

The cause of dispersion is that different colours of white light having different wavelengths deviate/bend through different angles  with respect to the incident ray on passing through a glass prism. That is why they split on coming out from the prism along different directions. The red light bends the least while the violet bends most and hence spectrum forms.

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