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Q.
What is the maximum number of emission lines obtained when the excited electron of a hydrogen atom in $ n=5 $ drops to the ground state?
J & K CETJ & K CET 2010Structure of Atom
Solution:
Number of spectral lines obtained when an electron drops from $n t h$ level to ground level $=\frac{n(n-1)}{2}$
$\therefore $ Number of emission lines obtained, when electron drops from $5th$ level to ground state
$=\frac{5(5-1)}{2}=\frac{5 \times 4}{2}=10$