1. Introduction

Light is a type of energy which can be visible to our human eyes. This visible light is made up of seven different colours of light; that is why the human eyes see seven different colours of light when the visible light passes through water of glass and that is what we call rainbow. Rainbow shows the entire spectrum of visible light in the order of violet, indigo, blue, green. yellow, orange and red which is also known as the 'visible spectrum'.

Visible spectrum and radiation is a small part of the electromagnetic spectrum and radiation given off by stars like the Sun. The study of light is known as “Optics”, which is an important research area in modern physics. But in additional to visible light, optics also dealt with invisible parts of the whole electromagnetic spectrum in which the visible spectrum is but a small portion in it. Overall, in physics, the term light actually refers as the electromagnetic radiations of any wavelength or frequency, whether it is visible or invisible.