Physics · Modern Physics / Principles and Exploration
Photoelectric effect — principles and investigation
Even if the light shines brighter, there are times when electrons do not come out. This is an experiment to find conditions for photoelectron emission by changing the type of metal, frequency, intensity, and stop voltage of light. By distinguishing between the maximum kinetic energy of one electron and the number of electrons emitted, the particle nature of light can be explained.
How does it work?
The frequency changes the maximum kinetic energy, and the strength above the threshold changes the number of electrons.
Kmax = hf − W · f₀ = W/h · eVs = Kmax
Try this investigation
- Electrons are emitted only when the photon energy exceeds the work function. Light intensity changes the number of electrons and saturation current, but does not change the maximum kinetic energy. If the reverse voltage is greater than the stop voltage, the collection current is zero.
- Press the standard conditions button, run it, and record each measurement value.
- Compare records with the same frequency but with only the intensity changed. The stop voltage value is the same as Kmax when energy is written in eV.
Interpreting your results
If the intensity of light above the threshold is doubled, what is the maximum kinetic energy?
Since Kmax=hf−W, the maximum energy is determined not by intensity but by frequency and work function of the metal.
Assumptions and limitations
It is an ideal model based on work function. All emitted electrons are simplified to have Kmax, and when the reverse voltage is greater than Vs, the current is displayed as 0. The actual energy distribution, surface condition, and collection efficiency are omitted. Kmax for each frequency is the maximum possible value, and there is no emission at intensity 0.