ABSTRACT
As seen in Figure 1.1, visible light is just a small part of the electromagnetic spectrum to which the human eye is sensitive and it includes waves with lengths from around 380 nanometers (10-9 m) to about 780 nanometers. On the lower energy side, the spectrum starts with radio waves used to transfer images and sound (like radio and television) and continues to microwaves, used in devices such as radar and ovens. Further down the spectrum are infrared waves, which are perceived as heat. On the higher-energy side of the visible spectrum with shorter wavelengths is ultraviolet radiation. Thus, X-rays are used in medicine for bone outlining; next are gamma rays and nally cosmic rays. Different regions of the electromagnetic spectrum are also presented in Appendix A.
