IR Receiver LED as the name suggests is used to detect Infrared Rays. IR Receiver LED is a photodiode that has a cathode and an anode similar to the normal LED.
 
IR Receiver has two leads the shorter one is a cathode and the longer one is an anode. An anode is the positive pin of the IR receiver while the cathode is the negative pin. IR Receiver is always connected in negative polarity i.e., Anode and Cathode are inversely connected to ground and supply voltage respectively.
 
When light falls on the IR Receiver LED it allows current to flow through it. The amount of current flow is directly proportional to the light falling on the IR Receiver LED. The Diameter of this IR Receiver LED is 5mm. Power dissipation (Pd) is 100mW.