Question

Which the following series fall in the visible range of electromagnetic spectrum of a hydrogen atom?

• A. Brackett series
• B. Lyman series
• C. Balmer series
• D. Paschan series

Answer 1

Answer: (C)

$\frac{1}{\lambda }=R\left[\frac{1}{n_f^2}-\frac{1}{n_i^2}\right]$
Balmer Series; $n_f=2;n_i=3,4,5,......$
$\frac{1}{\lambda }=1.097\times 10^{7}m=\left[\frac{1}{4}-\frac{1}{9}\right]$
$\Rightarrow \frac{1}{\lambda }=1.097\times 10^{7}m=\left[\frac{5}{36}\right]$
$\Rightarrow \lambda =\frac{36}{5}\times \frac{10^{-7}}{1.097}m$
$\Rightarrow \lambda =6.56\times 10^{-7}m$
$\Rightarrow \lambda =656\times 10^{-9}m$
This wavelength falls in visible range.