Indicate the reason for the white light's dispersion as it passes through a glass prism. How did Newton use two identical glass prisms to explain that the sun's white light contains seven colours? Draw a ray diagram to show the path of light when two identical glass prisms are arranged together in an inverted position with respect to each other, and a narrow beam of white light is allowed to fall obliquely on one of the focus of the first prism.

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What is meant by the term angle of deviation? When it passes through a triangular glass prism why do different components of white light split up into a spectrum? Show how the red colour deviates from white light when it goes through a prism.

When white light is incident on the first surface of a prism and enters in glass, the light of different colours, due to different speeds, gets reflected through different angles. Thus, the dispersion of white light into its constituent colours occurs at the first surface of the prism. Firstly, Newton made white light fall on a prism, which caused white light dispersion into seven colours. Then Newton placed an inverted prism in the path of the colour band of seven colours. As a result, only a beam of white light came out from the second prism. So, Newton concluded that white light comprises seven component colours.

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An emergent ray bends at an angle to the direction of the incident ray, and the angle between them is known as the angle of deviation. 

When a beam of light enters a prism, it refracts and splits into its seven constituent colours. The light ray splits because the different colours travel through a glass prism at different speeds. Hence, each colour passing through the prism bends at different angles to the incident beam, which gives rise to the formation of the colour spectrum.

The red colour will deviate the least because it has the highest wavelength among the seven lights and therefore has the minimum angle of deviation.