Determine maximum kinetic energy, in eV.

Question

Indigo light of wavelength 455nm is used in a photoelectric effect experiment that involves directing the light source at the selenium that has a work function of 1.5x10^-19J. Determine if any electrons are emitted, and if they are, determine their maximum kinetic energy, in eV.

Answer 1

The energy of photon with wavelength λ is: , where h is the Plank's constant and c is the speed of light. So when λ=455 nm, the photon energy is E=6.63×10^-34×3×10⁸ / 455×10^-9 = 4.37×10^-19 (J),

Since this energy is higher than the work function of Selenium, therefore there will be electron emission. And the maximum kinetic energy of the electron is the difference of the photon energy and the work function, which is 4.37×10^-19 - 1.5x10^-19 = 2.87x10^-19 J = 1.79 eV.