1  INTRODUCTION
Nature has endowed the human eye (retina) with the sensitivity to detect
electromagnetic waves within a small range of the electromagnetic
spectrum Electromagnetic radiation belonging to this region of the
spectrum (wavelength of about 400 nm to 750 nm) is called light It is
mainly through light and the sense of vision that we know and interpret
the world around us There are two things that we can intuitively mention about light from
common experience