The chapter begins with a basic discussion about the human eye, its construction, working, the function of the iris and pupil, and a brief account of rod and cone cells. An important discussion about how a normal eye can see distant and nearby objects is also included. Accommodation is defined as the ability of the eye to change its focal length to focus on far-off and nearby objects. The visual range of the normal human eye is from 25cm to infinity. The shortest distance that can see clearly without exertion is referred to as the least distance of distinct vision. This chapter includes the following defects of vision and their correction using different lenses:
The chapter clarifies the question that why do we have two eyes for vision and not just one? It also focuses on the importance of realizing that we have been blessed with the gift of vision, i.e. eyes. A triangular glass prism is a clear glass item comprising two triangular ends and three rectangular faces. We'll study the refraction of light through this glass prism. White light is made up of seven colours abbreviated by VIBGYOR. Dispersion is splitting. It is the phenomenon of the division of light into a band of seven colours passing a prism. Re- combination of this seven-coloured spectrum gives white light again. A rainbow is formed due to the process of dispersion in the atmosphere. The following phenomenon takes place due to atmospheric refraction:
Scattering of light is meant to throw light in random directions. This phenomenon is responsible for the Tyndall effect, the blue colour of the sky, and the red colour at sunrise and sunset. The colour of scattered light depends on the size of scattering particles. The chapter concludes with an experiment to study the scattering of light.