Question

What is the wavelength of the least energetic photon emitted in the Lyman series of the hydrogen atom spectrum?

• A. $150$ nm
• B. $122$ nm
• C. $102$ nm
• D. $82$ nm

Answer 1

The correct option is B $122$ nm

Least energetic transition for Lyman series is given by: $n=2$ to $n=1$

Wavelength corresponding to above transition is given by

$\frac{1}{\lambda }=R{Z}^2(\frac{1}{1^2}-\frac{1}{2^2})=10967800\times \frac{3}{4}{m}^{-1}$

$\Rightarrow \lambda =122nm$

Hence, the correct option is $B$