Electromagnetic wave phenomena cover a large range of wavelengths and associated frequencies, from radio waves to gamma rays and beyond. The radio bands for long distance transmission have wavelengths of kilometres and longer and frequencies of kHz to MHz. Television uses shorter wavelengths and higher frequencies. Room radiators emit heat in the form of infrared radiation. Visible light occupies a narrow range of wavelengths between 700 and 400 nm (nanometres). X rays and gamma rays were unknown when Maxwell formulated his equations.