[G]nomes come in two genders, as one might expect. The particles we consider “negatively charged” are male gnomes; positively charged particles are female. Gnomes are simultaneously an intensely homophobic and an intensely sexual species, and two gnomes of the same gender (or “charge,” as some physicists are wont to call it) repel each other strongly. Oppositely-gendered gnomes, however, experience a strong attraction. Given the gnome propensity for drunken orgies, this attractive force increases with the number of gnomes involved.
The behavior of light is best explained through gnome beer. Gnomes are voracious consumers of beer, and under certain conditions gnomes can be made to give up their beer, emitting light. This causes feature such as the photoelectric effect.