Electromagnetic spectrum

The electromagnetic (EM) spectrum is the range of all possible electromagnetic radiation. The "electromagnetic spectrum" (or just spectrum) of an object is the characteristic distribution of electromagnetic radiation from that object.

The electromagnetic spectrum, shown in the chart, extends from just below the frequencies used for modern radio (at the long-wavelength end) to gamma radiation (at the short-wavelength end), covering wavelengths from thousands of kilometers down to fractions of the size of an atom. In our universe, the short wavelength limit is likely to be the Planck length, and the long wavelength limit is the size of the universe itself, though in principle the spectrum is infinite.

The most familiar part of the electromagnetic spectrum is the visible region, which spans the colors of the rainbow (wavelength range of 400-700 nanometers (nm)). We are able to see things because our eyes are sensitive to this region of the spectrum. A variety of applications have been found for the different parts of the spectrum. For instance, radio waves are used for the transmission of data for television, mobile phones, and wireless networking. X-rays and gamma rays are used in medicine.