ABSTRACT
The electromagnetic (em) spectrum ranges from very short wavelength cosmic rays through X-rays, γ rays, ultraviolet (UV), visible, infrared to radiofrequency (RF) (11). The various types of em radiation differ with respect to their wavelength, which is simply the distance between the crests of the waveform (12). UV, visible and infrared radiation are collectively known as optical radiation. Light is, by definition, em radiation within the visible band.
