Welcome to the weirdness of physics. The first video should be review from chemistry (or science in general), but the next two videos explain the wave nature of light (as opposed to the particle model used in the photoelectric effect). The last three videos, hold on because that is where it gets good. Electrons have wavelength (?) YES, as does all matter, light has momentum (?) YEP, and the uncertainty principle, which says you can't know it all, because the universe isn't like that. Enjoy and Bon Appetit.