Question

A hydrogen atom in the ground state is excited by radiations of wavelength $975A$${}^0$. The Longest wavelength will be

• A. $18701.29$$A^0$
• B. $15622$$A^0$
• C. $19768$$A^0$
• D. $11973$$A^0$

Answer 1

The correct option is A $18701.29$$A^0$

longest wavelength is the minimum energy gap which must be between $n=3$ and $n=4$
$\frac{1}{\lambda }=1.1\times {10}^7\times 1^2[\frac{1}{3^2}-\frac{1}{4^2}]$
$=1.87\times {10}^{-6}m$ or $18701.29$ $A^o$
$E_1---------n=1$
$E_2---------n=2$
$E_3---------n=3$
$E_4---------n=4$