Final answer:
Threshold frequency is the minimum frequency required by light to eject electrons from a metal, influential in the study of the photoelectric effect and quantum mechanics.
Step-by-step explanation:
Threshold frequency in the context of photoemission is the minimum frequency that light must have in order to eject electrons from the surface of a metal. This phenomenon is part of the photoelectric effect, which helps us understand how light interacts with matter. If the frequency of incident light is below this threshold, no electrons will be emitted, regardless of the light's intensity or duration. The threshold frequency is directly proportional to the work function of the metal, which is the energy needed to release an electron from the surface of the material.
The significance of the threshold frequency lies in its direct relationship with the energy of the photons required to cause electron emission. Photons with frequencies higher than the threshold frequency will have sufficient energy to eject electrons, with any excess energy contributing to the kinetic energy of the ejected electrons. The concept of threshold frequency was critical in the development of quantum mechanics, supporting the idea that light can behave as both waves and particles.