Photoelectric Effect 1

What is the PHOTO-ELECTRIC EFFECT?
The photoelectric effect is the emission of electrons from the surface of a substance when light is shone onto it.



This does not happen for any type of light or metal.
Certain conditions must be met.

Study the ANALOGY.


To buy the goods, the incoming customer must have sufficient money to pay for the goods.
He can leave with change.

In a similar way, an incoming photon of light must have sufficient energy to "buy" (eject) an electron from the metal.
All the excess energy ("change") becomes the kinetic energy of the ejected electrons (photoelelctrons).
Easy!

Unrealistic values are used below, but the example is just to show you the names and relationships between the various energies.



For electrons to be emitted, the incoming light (photon) must have sufficient energy to overcome the work function of the metal to free the electrons.

These free electrons can now be used as electricity as in solar cells.



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