List three observations of the Photoelectric effect that support the Particle model of light.
1: Existence of a threshold frequency
2: Negligible time delay
3: The Maximum kinetic energy of photo electrons is independent of the intensity of light
Explain how the “Negligible time delay,” supports the particle model of light but rejects the wave model of light.
When light is incident on a metallic surface, photo electrons are ejected instantly (provided enough energy is supplied), indicating that the process of the electrons receiving energy to be released comes from the absorption of a particle such as a photon (which is an instant process). A wave however, is a continuous distribution of energy, and if this were how electrons received enough energy for ejection, then it would take time for electrons to be released if light is incident on the metallic surface.
Explain how the existence of a Threshold frequency supports the particle model of light but rejects the wave model of light.
In the photoelectric effect, a minimum frequency of incident light is required for electrons to be ejected and for a photo current to be produced. This contradicts the wave model of light, given a wave is a continuous distribution and supplies energy to electrons over a period of time. This implies any frequency of light will produce a photo current given sufficient time, which is not the case. Rather, this supports the particle model of light as photons have a discrete amount of energy (proportional to frequency)
Explain how the independence of Light’s intensity on the maximum kinetic energy of photo electrons supports the particle model of light but rejects the wave model of light.
In the photo electric experiment, it is shown how the intensity of light incident on a metallic surface has no effect on the maximum kinetic energy of photo electrons ejected. This supports the particle model of light as under this model changing the intensity of light incident on a metal changes the number of photons incident on the metal, which effects the amount of photo electrons ejected but not not their maximum kinetic energy. Per the wave model, increasing intensity causes a greater amount of energy that would be delivered to the delocalised electrons, which would increase the maximum kinetic energy of the photo electrons ejected, which is not displayed in this experiment.
