What is a Light-Emitting Diodes (LEDs)?

LEDs are semi-conductors that are used to emit radiation. In this instance, semi-conductors behave much like atoms and molecules do. They have energy levels and radiation is emitted when electrons fall from a higher level to a lower level. The difference is that an electric current is needed for this to happen. LEDs are much more energy efficient than lamps. They are not coherent, like lasers are, but emit only one wavelength. With some clever engineering, a multiwavelength LED source can be created, though.