If $\lambda_1$ and $\lambda_2$ are the wavelength of the photons emitted, when electrons in the $n^{\text…
- $\sqrt{\frac{2\left(\lambda_2-\lambda_1\right)}{2 \lambda_2-\lambda_1}}$
- $\sqrt{\frac{2 \lambda_2-\lambda_1}{2\left(\lambda_2-\lambda_1\right)}}$
- $\sqrt{\frac{4 \lambda_2-\lambda_1}{4\left(\lambda_2-\lambda_1\right)}}$
- $\sqrt{\frac{4\left(\lambda_2-\lambda_1\right)}{\left(4 \lambda_2-\lambda_1\right)}}$
Solution

We have,
$\lambda_1=\frac{h c}{\Delta E_{n \rightarrow 2}} \text { and } \lambda_2=\frac{h c}{\Delta E_{n \rightarrow 1}}$
$\begin{aligned} \Rightarrow & \quad \lambda_1\left(\frac{13.6}{4}-\frac{13.6}{n^2}\right) =\lambda_2\left(\frac{13.6}{1}-\frac{13.6}{n^2}\right) \\ \Rightarrow & n =\sqrt{\frac{4\left(\lambda_2-\lambda_1\right)}{4 \lambda_2-\lambda_1}}\end{aligned}$
Asked in: AP EAMCET 2018 (23 Apr Shift 2)