Photoelectric Effect

Photoelectric Effect

When light strikes a metal surface, electrons can be detected to be emitted from the surface. Since both light and electric charges are involved the term photoelectric effect was given to this phenomenon. The emitted electrons are called photoelectrons.

Photocell

Photocell experiments
- cathode is photosensitive,
- conduction occurs if light emits electrons from cathode.
- observations from this setup were used to explain the nature of light specifically to what extent does light behave as a continuous wave and to what extent does light behave as descrete packets of energy

	Predictions based on light behaving as a wave	Predictions based on light behaving as discrete packets (photons)
Effect of light intensity	The electons ejected from the surface of the metal should be released with greater KE since the amplitude of the light "wave" would be greater and have more energy.	More electrons would be ejected since a greater intensity would mean more photons
Effect of light frequency (colour)	The frequency of the light wave should not effect the KE of the emitted electrons, (since the energy of a wave depends on the square of the waves amplitude not its frequency.)	Max Planck hypothesized that each photon of light had a discrete amounts of energy which was proportional to the frequency of the light. (after studying the radiation spectra of blackbody radiation at various temperatures). E=hf If this were true a higher frequency light would impart a higher Ek to the photoelectron.

http://nobelprize.org/nobel_prizes/physics/laureates/1923/index.html

more on this lesson in notes not complete.

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