The expression for longest wavelength in Paschen series (for H atom) is 144R/x.

Question

The expression for longest wavelength in Paschen series (for H atom) is \(\frac{144R}x\). Find x.R is Rydberg’s constant.

Answer 1

Longest wavelength ⇒ Minimum energy

\(\frac 1\lambda =R\left[ \frac 1{3^2} - \frac 1{4^2}\right]\)

\(=\frac{7R}{144}\)

⇒ \(\lambda = \frac{144R}7\)