Question

Every series of hydrogen spectrum has an upper and lower limit in wavelength. The spectral series which has an upper limit of wavelength equal to $18752\stackrel{\circ }{A}$ is

• A. Balmer series
• B. Lyman series
• C. Paschen series
• D. Pfund series

Answer 1

The correct option is C Paschen series

$\frac{1}{\lambda }=R[\frac{1}{n_1^2}-\frac{1}{n_2^2}]]\Rightarrow \frac{1}{n_1^2}-\frac{1}{n_2^2}=\frac{1}{R\lambda }=\frac{1}{1.097\times {10}^7\times 18752\times {10}^{-10}}=0.0486=\frac{7}{144}But\frac{1}{3^2}-\frac{1}{4^2}=\frac{7}{144}\Rightarrow n_1=3and{n}_2=4\left(Paschenseries\right)$