Question

(a) What is meant by the dispersion of white light? Describe the formation of the rainbow in the sky with the help of a diagram.
(b)What is hypermetropia? Draw ray diagrams to show the image formation of an object by:
(i) Hypermetropic eye
(ii) Correction made with a suitable lens for the hypermetropic eye.

Answer 1

(a) The splitting of white light into seven colors on passing through a transparent glass prism is called dispersion of white light.

A rainbow is formed in the sky because of the dispersion of sunlight by millions of water droplets in the atmosphere. Every single water droplet behaves like a tiny glass prism that splits the white light into different colors. Different colors bend at different angles on passing through the water droplets, thus separating the white light into a natural spectrum of seven colors, as Violet, Indigo, Blue, Green, Yellow, Orange, and Red. The diagram below shows the formation of a rainbow:



(b) Hypermetropia or long-sightedness is a common eye defect, in which a person is not able to nearby objects whereas the farther objects appear clear to the person.

(i) Hypermetropic eye:



(ii) Correction made with a convex lens for the hypermetropic eye: