An infrared light emitting diode(IR LED)is a special purpose. LED Emitting infrared rays ranging 700nm to 1mm wavelength. Different IR LEDs may produce infrared light of different wavelengths, that just like different LEDs emitting different color.
IR LEDs are usually made of aluminum gallium arsenide or gallium. In order to complement with IR receivers, these are commonly used as sensors.
Generally,IR LED have the same appearance as a common LED. Because of the human eyes cannot see the infrared radiations, it is not possible for a person to identify if an IR LED is working. A camera on a cell phone solves this problem. The IR rays from the IR LED in the circuit are shown in the camera. So you can easy to see whether your IR LED is working or not!