Question

Light with a wavelength of 405 nm fell on a strontium surface, and electrons were ejected. If the speed of an ejected electron is 3.39 105 m/s, what energy was expended in removing the electron from the metal?
(1/2*m*v^2)= hc/wavelength)-phi
Solve for phi, the work function.
m = mass electrons.
v = speed electron
h = Planck's constant'
c = speed of light in m/s
wavelength in meters.
phi will be energy in J/photon.
how do you know what the mass electrons is?

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