NEET Physics Atomic Physics NEET PYQ-Atomic Physics

Hydrogen atom in ground state is excited by a monochromatic   radiation   of \[\lambda =975\,\overset{o}{\mathop{A}}\,\]. Number of spectral lines in the resulting spectrum emitted will be                                           [NEET 2014]

A) 3

B) 2

C)                  6

D) 10

Correct Answer: B

Solution :

Energy provided to the ground state electron

\[=\frac{hc}{\lambda }=\frac{6.6\times {{10}^{-34}}\times 3\times {{10}^{8}}}{975\times {{10}^{-10}}}\]

\[=\frac{6.6\times 3}{975}\times {{10}^{-16}}\]

\[=0.020\times {{10}^{-16}}=2\times {{10}^{-18}}J\]

\[=\frac{20\times {{10}^{-19}}}{1.6\times {{10}^{-19}}}eV\]

\[=\frac{20}{1.6}eV=12.5eV\]

It means the electron is jump to \[n=3\] from \[n=1\]. The number of field lines possible from \[n=3\]

To \[n=1\] is 2.

\[n\to 3,\] to \[n\to 2\] to \[n\to 1\]