Photoelectric Effect Calculator
Enter light frequency (or wavelength) and work function to compute the maximum photoelectron kinetic energy, threshold and stopping voltage.
Input Data
Results
At a glance:The photoelectric effect (Einstein, 1905): a photon of energy E_photon = h·f (or hc/λ) ejects an electron from a metal if E_photon > Φ (work function). The maximum kinetic energy of the emitted electron is K_max = h·f − Φ. The threshold frequency is f₀ = Φ/h (below it no emission, regardless of intensity); the threshold wavelength λ₀ = hc/Φ. The stopping voltage V_s that just halts the current satisfies e·V_s = K_max. This effect proved light's particle (photon) nature and won Einstein the Nobel Prize. This tool computes K_max, f₀, λ₀ and V_s from f (or λ) and Φ.
Formula
K_max = h·f − Φ
Threshold: f₀ = Φ/h, λ₀ = hc/Φ
Stopping: e·V_s = K_max
$$E = \frac{hc}{\lambda}$$$$KE_{\max} = \frac{hc}{\lambda} - \varphi$$$$\lambda_0 = \frac{hc}{\varphi}$$How to Use
- Enter light frequency f (or wavelength λ) and the work function Φ (eV).
- The calculator returns photon energy, K_max, threshold f₀/λ₀ and stopping voltage V_s.
Case Studies
Sodium surface
Φ = 2.28 eV, λ = 400 nm (E = 3.10 eV).
K_max = 3.10 − 2.28 = 0.82 eV.
V_s = 0.82 V; f₀ = 2.28 eV/h ≈ 551 nm threshold.
FAQ
Why doesn't brighter light below threshold work?
Each electron needs one photon with energy > Φ; a dim high-frequency light works, but bright low-frequency light never does (photon energy depends on frequency, not intensity).
What is the stopping voltage?
The reverse voltage that reduces the photocurrent to zero; e·V_s = K_max, so it directly measures the max electron kinetic energy.
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References
Content review: Calculatorism Science Team. Results are for reference only; please refer to the relevant authorities for the official figures.