The photoelectric effect refers to the phenomenon where certain materials, when exposed to light, emit electrons. This intriguing phenomenon was first discovered by Heinrich Hertz in 1887 and later explained by Albert Einstein in 1905. The understanding of the photoelectric effect played a crucial role in the development of quantum mechanics.

When light hits a material, it is made up of tiny packets of energy called photons. Each photon carries a specific amount of energy, depending on its frequency. If the energy of a photon is sufficient, it can transfer its energy to an electron in the material, causing the electron to be ejected from its atomic orbit.

This effect can be observed in a variety of situations. For example, when ultraviolet light shines on a metal surface, electrons are emitted, and this is the underlying principle behind the functioning of photocells or solar cells. Additionally, the photoelectric effect is used in devices like photomultiplier tubes and image sensors in digital cameras, enabling the detection and measurement of light.