Question

In $L{i}^{++}$, electron in first Bohr orbit is excited to a level by a radiation of wavelength $\lambda$. when the ion gets deexcited to the ground state in all possible ways (including intermediate emissions), a total of six spectral lines are observed. What is the value of $\lambda$ ?
(Given : $h=6.63\times {10}^{34}Js$; $c=3\times {10}^{8}m{s}^{-1}$)

• A. $9.4nm$
• B. $12.3nm$
• C. $10.8nm$
• D. $11.4nm$

Answer 1

The correct option is C $10.8nm$

$\Delta E=\frac{hc}{\lambda }$
$13.6\times 9-0.85\times 9=\frac{hc}{\lambda }$
$\lambda =\frac{hc}{9\times (13.6-0.85)eV}$
$=\frac{1240eV.nm}{9\times 12.75eV}$
$\lambda =10.8nm$