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

Answer 1

Answer: (C)

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