Describe the photoelectric effect. Name some devices that make use of this process.

Answer: The photoelectric effect is a phenomenon where light, usually ultraviolet or visible light, falls upon a material causing the ejection of electrons from its surface. It demonstrates the particle nature of light and forms the basis for several modern technologies. The work function (W) of a material is the minimum energy required to eject an electron from its surface. The threshold frequency (f₀) is the minimum frequency of light needed to eject electrons. The work function and threshold frequency are directly related, given by the equation W = h*f₀, where h is Planck's constant. The energy of an incident photon must be greater than or equal to the work function for the electron to be ejected, otherwise, the electron remains bound to the material.