Читать книгу Continuous Emission Monitoring - James A. Jahnke - Страница 133

Light emitting diodes are semiconductors that emit light when an electric current is applied. Light is emitted from the recombination of the electron–hole pairs of semiconductor materials. The light wavelength emitted is dependent upon the energy bandgap between the valence and conduction bands of the semiconductor and can range from the infrared to the ultraviolet region as the energy of the bandgap increases. LEDs are not lasers. They do emit over a spectrum narrower than incandescent sources, but the light emitted is incoherent.