An electric eye also called "magic eye" or, photocell, is a solid-state device that converts light into electrical energy by producing a voltage or uses light to regulate the flow of current. An electric eye, which automatically opens a door as you approach it, is an example of a photoelectric cell at work.
Could you please explain how the electric eye works in the above example in terms of the photoelectric effect?
Could you give another examples which use the same principle?