Final answer:
The phenomenon where light causes the emission of electrons from a metal surface is called the photoelectric effect, not the electromagnetic effect. It requires light with a frequency above the metal's threshold frequency to emit photoelectrons.
Step-by-step explanation:
The emission of electrons from a metal when light shines on it is not called the electromagnetic effect but rather the photoelectric effect. This phenomenon occurs when a metal surface is exposed to light of a certain minimum frequency, known as the threshold frequency. If the frequency of the incident light is above this threshold, the light's photons have enough energy to eject electrons from the metal surface. These emitted electrons are referred to as photoelectrons.
The discovery and explanation of the photoelectric effect were vital in the development of quantum mechanics. It highlighted that light has both wave-like and particle-like properties, contradicting the classical wave theory of light which predicted that the number of emitted electrons should depend on the light's intensity, not its frequency.