Free Photoelectric Effect Calculator
Calculate kinetic energy of emitted electrons using KE = hf - phi (Einstein's photoelectric equation).
nm
eV
Max Kinetic Energy
2.6599 eV
Photon Energy4.9599 eV
Threshold Wavelength539.1 nm
Max Kinetic Energy vs Photon Wavelength
Photoelectric Effect
Einstein explained that light consists of photons, each carrying energy E = hf. When a photon hits a metal surface, it can eject an electron if its energy exceeds the work function.
Formula
KE_max = hf - phi = (hc/lambda) - phi
where phi is the work function (minimum energy to free an electron). The threshold wavelength is lambda_0 = hc/phi.
Example Calculation
UV light at 250 nm hitting sodium (work function = 2.3 eV).
- 01E_photon = hc/lambda = (6.626e-34 * 3e8) / (250e-9)
- 02E_photon = 7.95e-19 J = 4.96 eV
- 03KE_max = E_photon - phi = 4.96 - 2.3
- 04KE_max = 2.66 eV
- 05Threshold: lambda_0 = hc/phi = 1240/2.3 = 539.1 nm
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