Final answer:
Einstein's explanation of the photoelectric effect in 1905 revealed the particle nature of light by introducing the concept of photons, leading to the development of quantum mechanics.
Step-by-step explanation:
Einstein's explanation of the photoelectric effect in 1905 brought about a new era of understanding in physics and chemistry regarding the quantum nature of light. He proposed that light should be seen as quanta of energy, now called photons, which exhibit both wave-particle duality. These photons have zero mass and carry a quantum of energy, described by the equation E = hv (where h is Planck's constant and v is the frequency of the light). The photoelectric effect, explained as the release of electrons by the absorption of photons, was an experiment that classical waveform theories of light could not explain. Einstein's work paved the way for the emergence of quantum mechanics and earned him the Nobel Prize in Physics in 1921.
While light can exhibit wavelike properties, as seen in interference patterns, it also displays particle-like properties, such as in the photoelectric effect, which were fundamentally incompatible with the classical wave concept of light. The energy of photons is quantized, meaning it can only be absorbed or emitted in discrete amounts, which was a revolutionary idea leading to our current understanding of electromagnetic radiation (EM radiation).
The photoelectric effect was one of several phenomena, including the Compton effect, that supported the particle theory of light. Compton's experiment further cemented the notion that EM radiation can behave as a stream of photons. These findings significantly altered the course of scientific thought, revealing that light possesses both wave and particle characteristics.