Earl's PhotoElectric Page

Equations to know:

E = hf

where E is the energy of a photon of
f is the frequency of light being shown
h is Planck's constant, or 6.626*10^-34j*s

E = KE_max + Wo

E is the energy of light put in
KE is the maximum Kinetic Energy of the electrons that are shot out- measured in Volts
Wo is the work function of the metal, or the amount of energy necessary to get the electrons out of the well (see diagram)

The Basics:

The photoelectric effect is Einstein's Nobel prize winning experiment. It says that as light of a certain frequency hits a metal, electrons are excited to the point where they jump out of the metal, and if directed into wire, cause a current.
There is a cutoff frequency where if the frequency is lower, no electrons will jump out of the metal. The amount of electrons that jump out of the metal depends on the work function of the metal and the frequency of the light used but is not dependent on the intensity, or amount of photons that strike the metal.

What this means:

This proved that light has a dual nature by also having particle characteristics, when originally in the debate between Huygens and Newton the consensus was that light was a wave since it could be diffracted.

SAMPLE PROBLEMS

1) Light of frequency 1.63*10¹⁵Hz is emitted onto a metal surface, and the electrons shoot out at a velocity of 2*10⁵m/s. Find the work function of the metal. (Mass of electron = 9.11*10^-31kg)

2) Explain why the photoelectric effect supports the theory that light is of a particle nature.

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