Final answer:
The photoelectric effect occurs when light of a specific frequency shines on the surface of some metals, causing the emission of electrons.
Step-by-step explanation:
The phenomenon observed when light of a certain frequency is allowed to shine on the surface of some metals is called the photoelectric effect. During the photoelectric effect, electrons are emitted or released from the metal surface. The emission of electrons occurs when the energy of the incident light (which is proportional to its frequency) surpasses a specific threshold frequency for the metal.