posted by Z .
Light of wavelength 272 nm shines on a piece of magnesium metal. What is the speed of the ejected electron? (Light energy greater than that of the work function of magnesium ends up as kinetic energy of the ejected electron. The work function is the minimum energy needed to eject an electron from the metal by irradiating it with light. The photoelectric work function for magnesium is 5.90 10-19 J.)
Energyphoton-workfunction=KE ejected electron
So what portion of this do you need help with? Consider Planck's equation.