Question

In a sample of H-atom, electrons make transition from 5th excited state to ground state, producing all possible types of photons. Then, number of lines in infrared region are:

• A. 4
• B. 5
• C. 6
• D. 3

Answer 1

Answer: (C)

6

Electron is in 5${}^{th}$ excited state i.e. $n=6$

Here transition from
$n=6\to n=1$
$n=5\to n=1$
$n=4\to n=1$
$n=3\to n=1$
$n=2\to n=1$,
lies in Lyman series (ultraviolet range)
$n=6\to n=2$
$n=5\to n=2$
$n=4\to n=2$
$n=3\to n=2$,
lies in Balmer series (visible range).
While,
$n=6\to n=3$
$n=5\to n=3$
$n=4\to n=3$
$n=6\to n=4$
$n=5\to n=4$
$n=6\to n=5$
these transitions lies in infrared region.
Option 'C' is correct.