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Explain the phenomenon of dispersion of white light through a glass prism, using suitable ray diagram.

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When the white light is passed through a pin, it get reduced to a narrow beam.
When this narrow beam is made to fall on a triangular glass prism and a white screen is held on the other side of the prism, we observe a band of seven colours on the screen. This phenomenon is called dispersion of white light.
Order of colours from bottom to top: remembering keyword VIBGYOR
V - Violet, I - Indigo, B - Blue, G - Green, Y - Yellow, O - Orange and R - Red.

Amount of scattering is inversely proportional to fourth power of wavelength.
The red colour (with maximum wavelength) bends the least on passing through the prism and violet colour (with minimum wavelength) bends through maximum angle on passing through the prism. This is why red is at top and violet is at bottom.
Thus, the phenomenon of splitting of white light into its constituent seven colours on passing through a glass prism is known as dispersion of light.

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