. E LECTROMAGNETIC S PECTRUM At the time Maxwell predicted the existence of electromagnetic waves, the only familiar electromagnetic waves were the visible light waves. The existence of ultraviolet and infrared waves was barely established. By the end of the nineteenth century, X-rays and gamma rays had also been discovered.
We now know that, electromagnetic waves include visible light waves, X-rays, gamma rays, radio waves, microwaves, ultraviolet and infrared waves. The classification of em waves according to frequency is the electromagnetic spectrum (Fig. . ).
There is no sharp division between one kind of wave and the next . The classification is based roughly on how the waves are produced and/or detected. FIGURE . The electromagnetic spectrum, with common names for various part of it.
The various regions do not have sharply defined boundaries. Electromagnetic spectrum