Applications of the photoelectric effect

A photocell is a vacuum tube with a concave cathode called an emitter, made from a material that emits electrons easily. When light of a frequency greater than the threshold frequency, shines on the emitter, electrons are released. The concave emitter focuses electrons on a thin wire anode called a collector. The thin anode does not block light. When the collector is at a positve potential, electrons are attracted to it.

The photocell is at the centre of the many applications of the photoelectric effect. It consists of a curved emitter and a rod as collector, so as not to inhibit light from reaching the emitter.


The structure of a typical photocell is shown below:
 

The flash of a camera uses the photoelectric effect
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Photocells are used in medicine. An example is shown in the diagram below:
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Photocells are used in garage door openers.
An example is shown in the diagram below:

Photocells are used in movie film. An example is shown in the diagram below:


Glossary