What is 'dispersion of white light' ? State its cause. Draw a ray diagram to show the dispersion of white light by a glass prism.
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Solution
The splitting of beam of white light into it seven constituent colours, when it passes through a glass prism, is called the dispersion of light.
When a beam of white light enters a prism, it gets refracted at a point and splits into its seven constituent colours (violet, indigo, blue, green, yellow, orange and red i.e., VIBGYOR). Different colours of light bend through different angles with respect to incident ray, as they pass through the prism. The red light bends the least while the violet the most. When a beam of sunlight is allowed to fall on one of the rectangular surfaces of the glass prism, we obtain a coloured spectrum with red and violet colour at its extremes