Calculator Inputs
Plotly Graph
The chart plots maximum kinetic energy against incident frequency using your calculated work function. When frequency crosses the threshold, photoelectrons gain positive kinetic energy.
Formula Used
Core Photoelectric Equations
Photon energy: E = hf = hc / λ
Einstein photoelectric equation: hf = φ + Kmax
From stopping potential: Kmax = eVs
Work function: φ = hf − eVs or φ = hc / λ − eVs
Threshold Relations
Threshold frequency: f0 = φ / h
Threshold wavelength: λ0 = c / f0
Energy conversion: 1 eV = 1.602176634 × 10−19 J
This calculator uses SI constants and converts the selected input units before performing each computation. Results are reported in both joules and electronvolts for easier lab interpretation.
How to Use This Calculator
Step 1: Choose the calculation mode that matches your known experimental values.
Step 2: Enter frequency or wavelength, then add either stopping potential or maximum kinetic energy if needed.
Step 3: Select units carefully. The calculator converts them internally before solving.
Step 4: Click the calculate button to show the result above the form.
Step 5: Review the graph, copy the derived threshold values, and export the summary as CSV or PDF.
Example Data Table
| Case | Known Input | Mode | Approx. Work Function | Approx. Threshold Wavelength |
|---|---|---|---|---|
| Example 1 | f = 1.30 × 1015 Hz, Vs = 1.20 V | Frequency + Stopping Potential | 4.176 eV | 296.9 nm |
| Example 2 | λ = 300 nm, Vs = 1.35 V | Wavelength + Stopping Potential | 2.783 eV | 445.5 nm |
| Example 3 | Threshold frequency = 5.50 × 1014 Hz | Threshold Frequency | 2.275 eV | 545.1 nm |
| Example 4 | Threshold wavelength = 660 nm | Threshold Wavelength | 1.879 eV | 660.0 nm |
Frequently Asked Questions
1) What is the work function in the photoelectric effect?
The work function is the minimum energy needed to remove one electron from a material surface. It is usually reported in electronvolts for convenience.
2) Why does stopping potential help find the work function?
Stopping potential gives the maximum kinetic energy of emitted electrons through Kmax = eVs. Once kinetic energy is known, the work function follows from Einstein’s photoelectric equation.
3) Can I use wavelength instead of frequency?
Yes. Since photon energy can be written as hc/λ, wavelength-based measurements work equally well when frequency is not directly available.
4) Why would a negative work function result appear?
A negative value usually means inconsistent inputs. Common causes are an incorrect unit choice, too large a stopping potential, or a kinetic energy larger than the photon energy.
5) What units does this calculator support?
It supports multiple frequency and wavelength units, plus kinetic energy in joules or electronvolts. Results are displayed in both joules and electronvolts.
6) Does this calculator include relativistic corrections?
No. It uses the standard introductory photoelectric model with accepted physical constants. That is the correct approach for most educational and laboratory problems.
7) What does threshold wavelength mean?
Threshold wavelength is the longest wavelength that can still eject electrons. Longer wavelengths have lower photon energy and cannot overcome the work function.
8) Can I use these results in a lab report?
Yes. The calculator is useful for checking calculations, summarizing inputs, and exporting a clean record. You should still cite your experiment setup and raw measurements separately.