The Bohr model of atoms

According to Bohr's hypothesis, electron can revolve only in those orbits in which its angular momentum is an integral multiple of h2π, where hbeing the Planck's constant. In these orbits, angular momentum of electron can have magnitude as h2π,2h2π,3h2π,…etc.. but never as 1.5 h2π,2.5 h2π,3.5 h2π, …etc. This is called the quantisation of angular momentum.