The BPW34 is a high speed Photodiode that is commonly used in control and driver circuits. Because of it's short switching time (20nS) it can be used in isolated data communication circuits and other remote communications like TV sets, dimmers and other equipments. Like all photo diode, the BPW34 is normally operated in series with a resistor and the current flowing though it depends on the amount of light falling on it. The intensity of light is measured in luminance. The below graph shows how the current flowing through the BPW34 Photodiode varies based on the light falling on it when the Reverse voltage (Vr) across the diode is 5V.
1 x BPW34 -Photodiode Through Hole