Final answer:
Einstein's particle theory of light explains the photoelectric effect by introducing photons, which interact with electrons individually. This theory solves the paradoxes that classical physics cannot, such as the immediate ejection of electrons, the independence of the electron's kinetic energy from light intensity, and the presence of a threshold frequency for electron emission.
Step-by-step explanation:
Classical Physics and the Photoelectric Effect
The classical wave theory of light posits that light's energy is proportional to its intensity and should be able to eject electrons if high enough, regardless of frequency. However, this does not explain several aspects of the photoelectric effect. First, there is no lag time between light exposure and electron emission. Second, the kinetic energy of photoelectrons does not increase with light intensity, contradicting the classical view that more intense light contains more energy. Lastly, there is a specific cut-off frequency below which no electrons are emitted, regardless of the light's intensity. These are contradictory to classical theory and indicate that energy is delivered in packets, or quanta.
In contrast, Einstein's particle theory of light explains the photoelectric effect by introducing photons, which are particles of light. Each photon has an energy related to its frequency (E = hv). According to this theory, an electron is ejected not because of cumulative energy over time, but because a single photon has the requisite energy to overcome the electron's binding energy. The number of ejected electrons depends on the number of photons, not the amplitude of the wave as classical physics would suggest.