Q.
The angular momentum of an electron in a Bohr's orbit of H− atom is 4.2178×10−34kg−m2/s . Number of spectral line emitted when electrons falls from this level to next lower level :-
Angular momentum mvr=2πnh=4.2178×10−34 ∴n=6.62×10−344.2178×10−34×2×3.14=4
when e⊖ falls from n=4 to next lower level n=3. Then only one spectral line will be obtained.