Q 12-12-050JEE MainJEE Main 2024 (27 Jan, Shift 2)Easy
If Rydberg's constant is $R$, the longest wavelength of radiation in Paschen series will be $\dfrac{\alpha}{7R}$, where $\alpha =$ ______.
Numerical value type. Enter your answer.
Answer: 144
The longest wavelength of the Paschen series is the $n = 4 \to 3$ transition:
$$\frac1\lambda = R\left(\frac19 - \frac1{16}\right) = \frac{7R}{144} \;\Rightarrow\; \lambda = \frac{144}{7R}$$
So $\alpha = 144$.
Solution by Sreeraj P, M.Sc Physics