Work function: The minimum energy required by a single electron to escape the metal surface.
Energy is needed to release the surface electrons because they are attracted by the electrostatic forces due to the positive metal ions.
Threshold frequency: The minimum frequency required to release electrons from the surface of a metal.
Hf = work function + KE(max)
Hf = work function + 1/2mv2(max)
f = work function / h
Shining light on a metal can release electrons but only if the light is of a high enough frequency. For most metals, this frequency is in the UV range. This is why if you shine a low frequency light on a metal (like a bright red light), the electrons will not be able to escape- the frequency isn’t high enough. In contrast, if you shine a high frequency light (like a UV lamp) on a metal, the electrons will be able to escape.
What actually happens?
Free electrons on the surface of the metal will absorb energy from the light which will cause them to vibrate. If it absorbs enough energy, the bonds keeping it on the metal will break and the electron will…