Let’s take a look at the experimental setup for studying the photoelectric effect.
At its most basic, we have two metal plates, called the emitter and the collector, housed in an evacuated tube. Outside the tube, the emitter and collector are connected through a micro-ammeter. When ultraviolet light is shone on the emitter plate, photoelectrons are liberated. Many of these photoelectrons will arrive at the collector, where they are reabsorbed. As long as the ultraviolet light keeps shining on the emitter, a continuous stream of photoelectrons will be travelling from the emitter to the collector, forming an electric current that can be read by the micro-ammeter. This current is known as the photoelectric current.
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xmPhysics 