Light-emitting diodes (LEDs) are semiconductor devices that emit light when an electric current passes through them. Initially used to produce a red indicator light in such things as electronic devices, LEDs are now available in a wide range of colours and light intensities.They can be found in traffic lights, automotive brake lights and headlights, Christmas lights, flashlights and cellphone screens, to name a few. More importantly, they are increasingly being used for general, white lighting in homes and businesses.