The angular momentum of an electron in the Bohr hydrogen atom is mur, where m is the mass of the electron, u, its velocity, and r, the radius of the Bohr orbit. The angular momentum can have only the values nh/2π, where n is an integer (the number of the Bohr orbit). Show that the circumferences of the various Bohr orbits are integral multiples of the de Broglie wavelengths of the electron treated as a matter wave.