Isaac Newton used the word spectrum in 1666 when he directed white sunlight through a glass prism. This experiment showed that light splits into seven distinct colors and can be recombined into pure white light.
James Clerk Maxwell developed four partial differential equations during the 1860s which predicted waves traveling at the speed of light. He inferred from this coincidence that light itself is an electromagnetic wave.
Paul Villard identified gamma rays while studying radioactive emissions from radium in 1900. William Henry Bragg later demonstrated that gamma rays are electromagnetic radiation rather than particles in 1910.
Radio waves span wavelengths indefinitely long on one end of the spectrum while microwaves measure about ten centimeters to one millimeter. Radio waves are emitted and received by antennas consisting of metal rod resonators.
Ultraviolet radiation irreparably damages complex DNA molecules by producing thymine dimers. Less than three percent of sunlight reaches sea level in ultraviolet bands due to absorption by the ozone layer.