Photoelectric Effect Lab: Change Light and Surface
Vary wavelength, work function, and intensity. Compare photon energy, electron energy, stopping potential, and an illustrative photocurrent.
Free, with no sign-up.
For High school students and adults reviewing the topic.
About 8 minutes.
How does it work?
- Change wavelength, work function, or relative intensity.
- Compare the paired presets below and above the emission threshold.
- Use the energy diagram and output table to check a challenge.
What will you get?
Separate the energy threshold for emission from the effect of intensity on current.
What does the model assume?
- Each photon frees at most one electron. Work function is a chosen surface parameter; no preset describes a named metal.
- The exact SI constants are h = 6.62607015 × 10⁻³⁴ J·s, c = 299792458 m/s, and e = 1.602176634 × 10⁻¹⁹ C. They give hc ≈ 1239.84198 eV·nm.
- Photon energy is hc divided by wavelength. The threshold wavelength is hc divided by the work function.
- When electrons are emitted, their maximum kinetic energy is photon energy minus work function. An energy of 1 eV corresponds to a stopping potential of 1 V for an electron.
- This idealized model gives emission only when photon energy exceeds the work function and intensity is positive. At the exact threshold it reports zero current.
- Relative intensity represents incident photon flux. Above threshold the illustrative current is proportional to it; below threshold increased intensity produces no emission.
- At zero intensity no electrons are emitted. Kinetic energy and stopping potential are then shown as unavailable, as they are below threshold.
- There is no contact potential, space charge, heating effect, or multiphoton emission.
Which setup would you like to try?
What can you change?
Range: 200 to 800 nm.
Range: 1 to 6 eV.
Range: 0 to 5 relative.
What does the model predict?
| Quantity | Value | Unit |
|---|---|---|
| Photon energy | 3.0996 | eV |
| Maximum emitted-electron kinetic energy | 0.5996 | eV |
| Stopping potential | 0.5996 | V |
| Threshold wavelength | 495.9368 | nm |
| Electrons emitted | Yes | |
| Photocurrent | 1.0000 | relative |
Can you reach these targets?
Use a 2.5 eV surface and 600 nm light at intensity 5. Check whether brightness overcomes the threshold.
- Target: Surface work function = 2.5 eV; tolerance 0 eV.
- Target: Light wavelength = 600 nm; tolerance 0 nm.
- Target: Incident intensity = 5 relative; tolerance 0 relative.
- Target: Photocurrent = 0 relative; tolerance 0 relative.
For a 2.5 eV surface under 400 nm light, raise intensity from 1 to 3 while preserving the maximum electron energy.
- Target: Surface work function = 2.5 eV; tolerance 0 eV.
- Target: Light wavelength = 400 nm; tolerance 0 nm.
- Target: Incident intensity = 3 relative; tolerance 0 relative.
- Target: Photocurrent = 3 relative; tolerance 0.01 relative.
- Target: Maximum emitted-electron kinetic energy = 0.5996 eV; tolerance 0.0001 eV.