What is ‘dispersion of white light’ ? State its cause. Draw a ray diagram to show the dispersion of white light by a glass prism.

Dispersion of White Light

The splitting of white light into its seven component colours (Violet, Indigo, Blue, Green, Yellow, Orange, and Red) when it passes through a refracting medium like a glass prism is called dispersion of light.

Cause of Dispersion

Different colours of light have different wavelengths and travel with different speeds in a medium like glass, although they travel with the same speed in vacuum/air. When white light passes through a prism, different colours bend through different angles with respect to the incident ray.

• Red light bends the least because it has the maximum speed in glass.
• Violet light bends the most because it has the minimum speed in glass.

This differential bending causes the constituent colours to emerge along different paths, making them distinct.

Ray Diagram

Below is the ray diagram showing the dispersion of white light by a glass prism:

``diagram {"xrange": [4.4, 475.6], "yrange": [-274.0, -26.0], "lines": [{"from": [150, -250], "to": [250, -50], "label": "Glass Prism"}, {"from": [250, -50], "to": [350, -250], "label": ""}, {"from": [50.0, -180.0], "to": [200.0, -150.0], "label": "White light beam"}, {"from": [200.0, -150.0], "to": [300.0, -140.0], "label": ""}, {"from": [200.0, -150.0], "to": [300.0, -170.0], "label": ""}, {"from": [300.0, -140.0], "to": [420.0, -120.0], "label": "Red (Bends least)"}, {"from": [300.0, -170.0], "to": [420.0, -220.0], "label": "Violet (Bends most)"}], "points": [{"x": 430.0, "y": -170.0, "label": ""}]} ``