photoelectric effect formulas and interpretation
The photoelectric effect ejects electrons when photon energy meets or exceeds a material’s work function.
The calculator preserves material presets and clearly reports when no electron emission occurs.
How to use the photoelectric effect calculator
- Choose a model: Select the relationship matching the problem.
- Choose the unknown: Select the quantity to calculate.
- Enter values: Enter all known values with matching units and signs.
- Calculate: Review the result, formula, units, and direction.
Formula and variables
Maximum emitted-electron kinetic energy equals photon energy minus the material work function.
Kmax = hc/λ − φ- Kmax — Maximum kinetic energy
- Highest emitted-electron energy (eV)
- h — Planck constant
- Quantum action constant (J·s)
- c — Light speed
- Vacuum light speed (m/s)
- λ — Wavelength
- Incident photon wavelength (nm)
- φ — Work function
- Minimum removal energy (eV)
Ultraviolet light example
Light of wavelength 250 nm strikes a metal with work function 2.5 eV.
- Wavelength
- 250 nm
- Work function
- 2.5 eV
- Eγ = 1239.84/250 ≈ 4.96 eV
- Kmax ≈ 2.46 eV
Result: Stopping potential is about 2.46 V.
Photon energy exceeds the work function, so emission occurs.
Understanding your results
Interpreting the result
The ideal equation reports maximum energy and ignores surface contamination and energy distributions.
Assumptions
- The selected equation represents the physical system.
- Inputs use a consistent reference direction.
- Values are converted through coherent SI units.
Limitations
- Vector components must be resolved along a common axis.
- External forces or energy losses are not added automatically.
- Results depend on the accuracy of entered measurements.
Common mistakes
- Mixing incompatible units.
- Dropping negative signs that represent direction.
- Using weight where mass is required.
- Entering a zero divisor.
Practical use cases
Physics problems
Check classroom, laboratory, and mechanics calculations.
Practical estimates
Estimate motion, forces, and energy for real systems.
Frequently asked questions
Can a result be negative?
Yes. For directional quantities, the sign indicates direction relative to the chosen positive axis.
Should I use SI units?
The interface can convert supported units, while the formulas are evaluated through coherent SI units.
Sources and review
- SI Brochure, 9th edition — BIPM. Accessed 2026-07-11.
- Special Publication 811 — NIST. Accessed 2026-07-11.
Reviewed 2026-07-11.