Graham's law

Graham's law states that the rate of effusion of a gas is inversely proportional to the square root of its molecular weight. Thus, if the molecular weight of one gas is four times that of another, it would diffuse through a porous plug or escape through a small pinhole in a vessel at half the rate of the other. A complete theoretical explanation of Graham's law was provided years later by the kinetic theory of gases. Graham's law provides a basis for separating isotopes by diffusion a method that came to play a crucial role in the development of the atomic bomb.

Well, it's an important theorem and a law for science students especially for science students in grade XI if they are in Nepal's college.