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

(a) The phenomenon of splitting white light into its components colours (violet, indigo, blue, green, yellow, orange, and red) while passing through a transparent medium like glass prism is known as the dispersion of light.

Process of the formation of the rainbow in the sky.

When the sun is shining and it's raining at the same time, then a rainbow is formed in the sky due to the dispersion of white sunlight by millions of raindrops (or, water droplets) in the atmosphere. Each raindrop behaves like a tiny glass prism that splits the white light into a spectrum (different colours). Different coloured rays present in white light are refracted or bend at different angles on passing through the water droplets. Thus the white light gets separated into a natural spectrum of seven colours, namely, violet, indigo, blue, green, yellow, orange and red (VIBGYOR). The diagram given below supports the above explanation and gives a clear picture of the formation of a rainbow. 

(b) Hypermetropia, or Long-sightedness, is a defect of vision because of which a person cannot see nearby objects clearly but has normal distant vision.

(i)  The ray diagram showing a hypermetropic eye.

(ii) The ray diagram showing the correction of the hypermetropic eye by using a suitable lens.

 Explanation

 Hypermetropia, also known as long-sightedness or far-sightedness, is a defect of vision in which a person can't see the nearby object clearly (appears blurred), though can see the distant objects clearly. The near point of a hypermetropic eye is more than 25 cm away.

This defect occurs either due to the low converging power of the eye lens, (because of its large focal length). Or, due to the eye-ball being too short, which causes light to focus beyond the retina, instead of directly on the retina. 

It is corrected by using spectacles containing convex lenses, which should be of such a focal length (or power) that it forms a virtual image of the object (lying at the normal near point N of 25 cm) at the near point 'N' of the hypermetropic eye.