An Infrared light-emitting diode (IR LED) is a type of electronic device that emits infrared light not visible to the naked eye.
The wavelength and colour of the light produced depend on the material used in the diode. Infrared LEDs use material that produces light in the infrared part of the spectrum, that is, just below what the human eye can see. Different infrared LEDs may produce
infrared light of differing wavelengths, just like different LEDs produce light of different colours.
Since the human eye cannot see the infrared radiations, it is not possible for a person to identify whether the IR LED is working or not, unlike a common LED. To overcome this problem, the camera on a cell phone can be used. The camera can show us the IR rays being emanated from the IR LED in a circuit.