SIMPLIFIED: "6.3: Photoelectric Effect"

Link to article: https://phys.libretexts.org/Bookshelves/University_Physics/University_Physics_(OpenStax)/University_Physics_III_-_Optics_and_Modern_Physics_(OpenStax)/06%3A_Photons_and_Matter_Waves/6.03%3A_Photoelectric_Effect 

Note: The image above was taken from the original article.

The article linked above talks about the photoelectric effect! In my opinion, this is one of the most fascinating topics in physics, and the photoelectric effect is usually taught with nuclear physics. Here is basically what it is: by shining a light (photons) onto certain metals, the electrons in the metal will absorb the photon energy, and if the electrons have sufficient energy, then it will cause the electron to break free and escape the metal. 

The remaining kinetic energy (which is excess energy) will contribute to the electron’s velocity after escaping. Ultimately the electrons need to gain enough energy to escape the metal, and then any energy remaining becomes kinetic energy.

It is important to note that photon energy is only affected by frequency, so using a brighter light (more photons per second, also known as intensity of light) does not change the amount of energy that is given to the electrons in the metal.

The article linked above deals with an equation related with the photoelectric effect, which we will not be covering here. However, we will let you know that the equation includes the work function, which is the minimum amount of energy needed for an electron to escape a metal.