Find the angular momentum of an electron in the hydrogen atom (initially in ground state) after it absorbs a photon of energy 12.1eV.

When an electron absorbs energy of 12.1 eV, it goes to third orbit. And we know that the angular momentum of electron in nth orbit is given by L=nh2π⇒Lf=3h2π=3×6.625×10-342×πJs=3.16×10-34 JsLi=h2π=1.05×10-34 JsTherefore ∆L=Lf -Li =2.11×10-34 Js