What phenomenon describes the emission of electrons when light hits a material?

The emission of electrons when light strikes a material is accurately described by the photoelectric effect. This phenomenon occurs when photons, or light particles, collide with electrons in a material, usually metals, and transfer enough energy to dislodge these electrons from the atomic structure of the material.

The crucial aspect of the photoelectric effect is that it demonstrates the particle-like properties of light. Specifically, it shows that light must have a certain threshold frequency or energy to release electrons from the material. If the energy of the photons is below this threshold, no electrons will be emitted regardless of the intensity of the light. This phenomenon has been pivotal in confirming the quantum theory of light.

The other options, while related to different physical principles, do not pertain to the emission of electrons due to light exposure. The photochromic effect refers to the reversible change in color of materials due to light exposure, thermal emission involves the release of energy as heat, and electromagnetic induction relates to the generation of voltage in a conductor within a changing magnetic field. These concepts are distinct and do not involve the direct emission of electrons as a result of light interaction.