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2.33    What transition in the hydrogen spectrum would have the same wavelength as the Balmer transition n = 4 to n = 2 of \textup{He}^+ spectrum?

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For the transition of H-like particles, 

\vartheta = \frac{1}{\lambda} = R_{H}Z^2\left [ \frac{1}{n_{1}^2}-\frac{1}{n_{2}^2} \right ]

For \textup{He}^+ transition spectrum,

Z=2,  n_{2}=4,  and n_{1}=2

Therefore,

 \vartheta = \frac{1}{\lambda} = R_{H}2^2\left [ \frac{1}{2^2}-\frac{1}{4^2} \right ] = \frac{3R_{H}}{4}

Then for the hydrogen spectrum,

\vartheta = \frac{3R_{H}}{4}   and   Z=1

Therefore, 

\vartheta = \frac{1}{\lambda} = R_{H}\times1\left [ \frac{1}{n_{1}^2}-\frac{1}{n_{2}^2} \right ]

\Rightarrow R_{H}\times1\left [ \frac{1}{n_{1}^2}-\frac{1}{n_{2}^2} \right ] = \frac{3R_{H}}{4}

\Rightarrow \left [ \frac{1}{n_{1}^2}-\frac{1}{n_{2}^2} \right ] = \frac{3}{4}

The values of n_{1}\ and\ n_{2} can be found by the hit and trial method in the above equation.

So, we get n_{1} = 1 and n_{2} = 2, i.e., the transition is from n =2 to n =1.

Posted by

Divya Prakash Singh

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