The photoelectric effect, initially observed by Heinrich Hertz in the late 19th century, posed a challenge to classical physics. It demonstrated that light behaves as both particles and waves, leading to the development of quantum theory. Albert Einstein's explanation of the photoelectric effect played a crucial role in advancing our understanding of light and its interaction with matter.

Einstein proposed that light is composed of discrete packets of energy called photons. According to his theory, when a beam of light shines on a metal surface, each photon interacts with an electron in the metal. If the energy of the photon is sufficient to overcome the binding energy holding the electron in the metal, the electron is ejected, creating a current known as the photoelectric current.

Einstein's explanation of the photoelectric effect provided a comprehensive framework for understanding experimental observations and paved the way for the development of quantum mechanics. By attributing the particle-like behavior of light to photons, he successfully explained phenomena that classical wave theory couldn't account for.

To illustrate this concept further, let's consider an analogy. Imagine a marble rolling up a hill. In classical physics, the marble's energy would gradually increase as it climbs higher. However, according to Einstein's theory, the marble can only reach the top if it possesses enough energy to overcome the hill's height. Similarly, in the photoelectric effect, electrons can only be ejected if they receive photons with energy greater than the binding energy of the metal.