Final answer:
Albert Einstein's explanation of the photoelectric effect introduced the concept of photons—quantized energy particles of light—leading to a new understanding of light as exhibiting wave-particle duality. This theory explained why light below a certain threshold frequency cannot eject electrons from a metal surface, which classical physics could not account for.
Step-by-step explanation:
Einstein and the Photoelectric Effect
Classical physics was unable to explain the photoelectric effect as it predicted that light, regardless of its frequency, could eventually provide enough energy to eject electrons from metal given enough time. Contrary to this, Albert Einstein utilized the particle theory of light to elucidate the photoelectric effect, suggesting that light consists of quanta, now known as photons, which carry discrete amounts of energy. This energy is directly proportional to the light's frequency, represented by the equation E = hf, where E is the energy of a photon, h is Planck's constant, and f is the frequency of the electromagnetic radiation.
Einstein's revolutionary idea was that each photon must have enough energy to overcome the electrostatic forces holding the electron to the metal, quantified as the work function of the metal. If the photon's energy is greater than this work function, the excess energy is imparted to the ejected electron as kinetic energy. This explained why no electrons are ejected if the incident light's frequency is below the metal's threshold frequency, regardless of light intensity, refuting the classical wave-only theory of light. Einstein's contribution to the photoelectric effect was pivotal in establishing the concept of wave-particle duality in quantum physics.