The Photoelectric Effect
Electrons are emitted from the surface of a metal when it’s exposed to light. This is called thephotoelectric effect. Each metal has a certain threshold frequency of light, below which nothing happens. Right at this threshold frequency, an electron is emitted. Above this frequency, the electron is emitted and the extra energy is transferred to the electron.
The equation for this phenomenon is
where KE is the kinetic energy of the emitted electron, h=6.63×10−34J⋅s is Planck’s constant, ν is the frequency of the light, and ν0 is the threshold frequency of the metal.
Also, since E=hν, the equation can also be written as
where E is the energy of the light and E0 is the threshold energy of the metal.
What is the threshold frequency ν0 of cesium?
Note that 1 eV (electron volt)=1.60×10−19 J.