Photoelectric Effect Virtual Experiment

Apparatus

Running

1Cathode metal

Work function φ: 2.28 eV
Threshold wavelength λ₀: 543.8 nm

2Light source

Wavelength λ

This wavelength is ultraviolet and invisible; the colour shown is symbolic.

Light frequency f: 9.99 × 10¹⁴ Hz
Photon energy: 4.13 eV

Light power on the cathode

At fixed power, longer wavelengths deliver more photons.

3Circuit

Anode voltage relative to cathode

Positive accelerates electrons to the anode · negative is a retarding voltage

4Run and record

5Analysis

Photon energy $E = h f$: 4.133 eV
Threshold frequency f₀: 5.51 × 10¹⁴ Hz
Maximum kinetic energy $K_{ma x}$: 1.853 eV
Stopping voltage Vs: 1.853 V
Maximum electron speed: 8.07 × 10⁵ m/s
Photon arrival rate: 1.21 × 10¹⁶ s⁻¹
Quantum efficiency (electrons per photon): 7.74 × 10⁻⁴
Saturation current: 1.50 µA

The energy relations (E = hf, Kmax = hf − φ) are exact. Quantum efficiency uses a simplified model (Fowler's quadratic onset near threshold) with a realistic magnitude for clean metals.

Move the wavelength towards the threshold and see where the current stops!

Current versus voltage

Maximum kinetic energy versus frequency

Experiment status

Every emitted electron reaches the anode; the current is saturated.

Circuit current: 1.50 µA
Electrons reaching the anode: 100 %
Threshold wavelength λ₀: 543.8 nm
Electron emission: Yes

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