The photoelectric effect, when electrons are ejected from the surface of a metal exposed to EM radiation, can refer to photoemission. Photoemission is when photons of sufficient energy can eject electrons from the surface of materials.

The photoelectric effect is evidence for the particle model of light. This is because each photon contains a discrete amount of energy, and each photon ejects one electron.

The following relationship links the frequency and energy of a photon, with Planck’s constant, and can be used to solve problems involving those quantities.

$$ E=hf $$

The threshold frequency is the minimum frequency of a photon required for photoemission, it is denoted by $f_o$.

The work function of a material is the minimum energy of a photon required to cause photoemission.

The following relationships can be used to solve problems involving the mass, maximum kinetic energy and speed of photoelectrons, the threshold frequency of the material, and the frequency and wavelength of the photons.

$$ E_k=hf-hf_o $$

$$ E_k=\dfrac{1}{2}mv^2 $$

$$ v=f\lambda $$