1. Emission of Electrons: According to the wave model, light is a continuous wave, and its intensity determines the brightness of light. However, in the photoelectric effect, electrons are emitted from the metal surface only when the incident light has a certain minimum frequency, known as the threshold frequency. This frequency dependence cannot be explained by the wave model.
2. Maximum Kinetic Energy: The wave model predicts that the maximum kinetic energy of emitted electrons should increase with the intensity of light. However, experiments show that the maximum kinetic energy depends solely on the frequency of light and is independent of its intensity.
3. Instantaneous Electron Emission: The wave model suggests that electrons should absorb energy gradually from the light waves over time until they reach enough energy to be emitted. This would result in a gradual increase in the number of emitted electrons with increasing light intensity. However, observations show that electrons are emitted almost instantaneously upon illumination, regardless of the intensity of light.
4. Absence of Time Delay: According to the wave model, it should take some time for electrons to absorb enough energy from the light waves and be emitted. This would lead to a measurable time delay between the incidence of light and the emission of electrons. However, experiments have demonstrated that electrons are emitted immediately without any noticeable time delay.
5. Particle-like Behavior: The photoelectric effect clearly demonstrates the particle-like behavior of light, where light interacts with electrons as discrete quanta of energy called photons. Each photon carries a specific amount of energy, and when its energy is equal to or greater than the work function of the metal, it can eject an electron from the surface.
These observations and experimental results contradict the predictions of the wave model of light and require a particle-like description of light, which is explained by the quantum theory of light, also known as quantum mechanics.
