Question

Is there a formula to find the maximum speed of emitted electrons?

Answer 1

Like from a surface? ie photoelectric effect?

Einstein equation is

\[ K = h\nu - \phi\]
\[ K = \frac{mv^2}{2}\]
h = Planck's constant
\[ \nu\] nu is frequency of radiation the electron is absorbing.

phi = work function, a property of the material the electron is being emitted from; the amount of energy it takes for an electron to be lifted from a surface. Can be written as
\[ \phi = h\nu_o\]
nu_o is the minimum frequency of radiation that has to strike the surface to lift an electron. Again, a property of the material.
Max velocity for a given interaction is then
\[ v_{max}^2 = \frac{2h(\nu - \nu_o)}{m_{e^-}}\]

That help ?