Why does the photoelectric effect cannot be explained by classical physics?

Hint: The photoelectric effect is a phenomenon that occurs when light strikes a metal's surface and causes electrons to be expelled from its surface. These expelled electrons are referred to as photoelectrons. It is vital to note that the emission of photoelectrons and the kinetic energy of the expelled photoelectrons are affected by the frequency of the incoming light on the metal's surface. Photoemission is the process by which photoelectrons are emitted from the surface of a metal as a result of the action of light.

Complete step by step solution:
The major issue is that the photoelectric effect includes the excitation of electrons into the conduction band, resulting in a charge flow, or current. According to a traditional view, current flow is determined solely by the strength of incident electromagnetic radiation, not by its frequency. However, it was discovered that there was a cut-off frequency below which no current flowed regardless of the intensity of the incident radiation.
Einstein's solution to this conundrum was that electromagnetic energy arrived in little packets (which we call photons) and that the energy of those small packets was inversely proportional to frequency. If the photons had insufficient energy (that is, the frequency was too low), no electrons would be emitted regardless of how many were delivered. It is important to remember that Einstein expanded on Max Planck's theory that light may be quantized as particles. There were other flaws with the classical model that were resolved, most notably the aptly termed "ultraviolet catastrophe." Einstein received the Nobel Prize for his theory.
It should be noted that the particle nature of light was not entirely novel. It had been around for quite some time (Newton believed in a type of light particle called a corpuscle). However, with the huge success of James Clerk Maxwell's equations, which were very much a classical model based on wave theory, particle models of electromagnetic theory had fallen out of favor. As a result, the quantum mechanical model for light was a dramatic departure, and, unlike Newton's model, it presented a theory supported by rigorous mathematics.


Note:Photoelectric applications:
Solar panels are used to generate electricity. These panels have metal combinations that allow for the generation of energy from a wide variety of wavelengths.
Sensors for Motion and Position: A photoelectric substance is placed in front of a UV or IR LED in this situation. When an object is placed between the light-emitting diode (LED) and the sensor, the light is turned off, and the electronic circuit detects a change in potential difference.
Illumination sensors, such as those found in smartphones, allow for automatic changing of screen brightness based on ambient lighting. This is because the quantity of the current created by the photoelectric effect is proportional to the intensity of light hitting the sensor.