It was suggested in another post that we have an MCAT chat. In addition, I propose a few topic discussions, because I'm sure that some people here have some great perspectives on material that may help. The photoelectric effect was mentioned in another thread, so I'll start this ball rolling: There are a few simple rules to follow: Start with the name: photoelectric effect. A photon goes in and an electron is ejected. In order to eject the electron, the energy of the incident photon must exceed the energy needed to eject the electron (called the binding energy to a chemist or work function to a physicist). Any energy beyond the threshold amount belongs to the electron in the form of kinetic energy. I am going to steal an analogy from the Berkeley Review general chemistry notes, so my apology to the author of their materials... take it as a compliment that your analogy works well. Just as money can be added to a vending maching to get a product, energy can be added to a material to get an electron. Vending machines only accept money in $0.05 increments, making the machine quantized (it won't take 42.3 cents, only amounts divisible by 5). From there, consider a $0.75 candy bar. You can add money to achieve one of three states. 1. Not enough money to get the item. The machine will hold the money until the coins are released. This is similar to adding energy to an atom (or molecule), but not enough to ionize it. An electron is excited, but the energy is released when the electron returns to its original ground state. 2. Just enough energy is added to ionize the material (exactly $0.75 has been added). or 3. More than $0.75 has been added. The machine will release the item and give back change (in a perfect world at least). This is analogous to the photoelectric effect. If the incident photon is of greater energy than the binding energy (work function), then an electron is ejected (ionized) and it gets the excess energy (change if you will) in the form of kinetic energy. With more money in the vending machine, you get more change. With more energy in the incident photon, the ejected electron gets more kinetic energy. Either way though, the candy bar is still $0.75 and the electron only costs a certain amount of energy (the binding energy). This works best with metals, because they have low ionization energies, which means they have low binding energies. Hence, shining light of a high enough frequency on the surface of a metal will eject an electon. The surface is better for losing an electron than the core, because an electron on the surface has fewer neighboring atoms and thus is held least tightly. This is the principle behind solar cells, where incident sunlight ejects an electron, which then travels from the anode (site of electon loss) to the cathode (sight of electron storage/reduction). I hope this perspective helps. Additions are strongly welcomed.