The Electromagnetic SpectrumThe electromagnetic spectrum consists of the full range of known electromagnetic waves, including gamma rays, X-rays, ultraviolet light, visible light, infrared light, microwaves, and radio waves. All of these are produced by various forms of oscillating charges or currents. Electromagnetic waves are transverse waves which travel at the speed of light and involve oscillating electric and magnetic fields at right angles to each other.Gamma RaysGamma rays are the most energetic known form of electromagnetic radiation, with frequencies of 3*1019Hz (30 EHz) or higher and wavelengths of 10-11m (10 pm) or lower. They are produced from the decay of excited nuclei of radioactive elements. Gamma rays can penetrate through several centimeters of lead and large doses of them are harmful.X-raysX-rays have frequencies ranging from 3*1016to 3*1019Hz (30 PHz to 30 EHz) and wavelengths from 10-11m to 10-8m (10 pm to 10 nm). X-rays penetrate easily through some materials such as fat and muscle but not others such as bone, which makes them useful in medicine. Medical X-rays are produced by colliding high-energy electrons into a metal target, usually tungsten.Ultraviolet LightUltraviolet (UV) light is light with higher frequency (lower wavelength) than visible light. UV light has frequencies ranging from 8*1014to 3*1016Hz (800 THz to 30 PHz) and wavelengths from 10-8m to 3.8*10-7m (10 nm to 380 nm). Prolonged exposure to UV light causes sunburn and can cause skin cancer. The earth's ozone layer absorbs most of the incoming UV light from the sun.Visible LightBy definition, visible light is light we can see. Visible light has frequencies ranging from 4*1014Hz to 8*1014Hz (400 THz to 800 THz) and wavelengths from 3.8*10-7m to 7.5*10-7m (380 nm to 750 nm). Red light has the lowest frequency (longest wavelength) and violet light has the highest frequency (shortest wavelength) of visible light. White light is composed of the colors of the rainbow, each of which has a unique frequency or wavelength, as can be seen by diffracting white light through a prism.Infrared LightInfrared (IR) light is light with lower frequency (higher wavelength) than visible light. IR light has frequencies ranging from 3*1011to 4*1014Hz (300 GHz to 400 THz) and wavelengths from 7.5*10-7m to 10-3m (750 nm to 1 mm). Infrared light is emitted from all objects at or near room temperature in the form of blackbody radiation.MicrowavesMicrowaves have frequencies ranging from 3*109to 3*1011Hz (3 GHz to 300 GHz) and wavelengths from 10-3m to 10-1m (1 mm to 100 mm). Excitations from microwaves cause many molecules such as water to oscillate and heat up, which is how microwave ovens work. The primordial big bang radiation discovered by Penzias and Wilson in 1965 is in the microwave region.Radio WavesRadio waves have frequencies ranging from 3*101to 3*109Hz (30 Hz to 3 GHz) and wavelengths from 10-1m to 107m (100 mm to 10,000 km). Radio waves are produced from the alternating current of an LC circuit. Radio waves carry information through modulation. Radio, television, cell phones, and remote controls all use radio waves.