Photoelectric Effect Calculator Formula
Understand the math behind the photoelectric effect calculator. Each variable explained with a worked example.
Formulas Used
Photon Energy
photon_energy = 6.626e-34 * 299792458 / (wavelength_nm * 1e-9) / 1.602e-19Max Kinetic Energy
ke_max = 6.626e-34 * 299792458 / (wavelength_nm * 1e-9) / 1.602e-19 - work_functionThreshold Wavelength
threshold_wavelength = 6.626e-34 * 299792458 / (work_function * 1.602e-19) * 1e9Variables
| Variable | Description | Default |
|---|---|---|
wavelength_nm | Photon Wavelength(nm) | 250 |
work_function | Work Function(eV) | 2.3 |
How It Works
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.
Worked Example
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
Frequently Asked Questions
What is the work function?
The minimum energy needed to remove an electron from a metal surface. It varies by material: cesium ~2.1 eV, sodium ~2.3 eV, copper ~4.7 eV, platinum ~6.4 eV.
Why was the photoelectric effect important in physics?
It proved that light has particle properties (photons), a key insight in quantum mechanics. Einstein won the Nobel Prize in 1921 for this explanation.
What happens if photon energy is less than the work function?
No electrons are emitted, regardless of light intensity. Increasing intensity sends more photons but each one still has insufficient energy.
Ready to run the numbers?
Open Photoelectric Effect Calculator