WE all know that light is made up seven different colour which can be remember as VIBGYOR . and when the light passes from a prism, due to different wave length and different speed of different colour of light all colour bent to different extent and when they will come out from prism we will get a band of seven colour which is known as spectrum. and the phenomena due to which white light splits up into seven different colour is known as dispersion of light.

                  Now this spectrum which lie between red and violet which is visible to us is a very small portion og electromagnetic spectrum. experiments show that this spectrum does not end only on this visible spectrum but it lie beyond this spectrum and is not visible to us and this part of spectrum is known as invisible spectrum.the complete wave of electromagnetic radiation are given below in order of their increasing wavelength and decreasing frequency. is given below

gamma rays    X rays    Ultra violet ray     visible light      Infrared     microwave      radiowave