1) The kinetic energy of an electron in the second Bohr orbit of a hydrogen atom is [a0, is Bohr radius] A) h24π2ma20 B) h216π2ma20 C) h232π2ma20 D) h264π2ma20 Answer: Option CExplanation:According to Bohr's model mvr=nh2π| ⇒ (mv)2=n2h24π2r2 ⇒ KE=12mv2=n2h28π2r2m......(i) Also Bohr's radius for H-atom is r=n2a0 Substiuting 'r' in equation (i) gives KE=h28π2n2a20m wher n=2, KE=h232π2ma20