The hydrogen spectrum consists of several spectral lines in Lyman series and Balmer series energy ratio question
Q. The hydrogen spectrum consists of several spectral lines in Lyman series (L1, L2, L3 … ; L1 has lowest energy among Lyman series). Similarly it consists of several spectral lines in Balmer series (B1, B2, B3 … ; B1 has lowest energy among Balmer lines). The energy of L1 is x times the energy of B1. The value of x is _____ × 10−1.

(Nearest integer)

Correct Answer: 54

Explanation

For hydrogen atom, energy of emitted photon is given by

\[ E = 13.6\left(\frac{1}{n_1^2}-\frac{1}{n_2^2}\right)\ \text{eV} \]

Energy of L1 (Lyman series):

For Lyman series, transitions end at \(n_1 = 1\).

For L1, the transition is from \(n_2 = 2 \to n_1 = 1\).

\[ E_{L_1} = 13.6\left(1-\frac{1}{4}\right) \]

\[ E_{L_1} = 13.6 \times \frac{3}{4} \]

\[ E_{L_1} = 10.2\ \text{eV} \]

Energy of B1 (Balmer series):

For Balmer series, transitions end at \(n_1 = 2\).

For B1, the transition is from \(n_2 = 3 \to n_1 = 2\).

\[ E_{B_1} = 13.6\left(\frac{1}{4}-\frac{1}{9}\right) \]

\[ E_{B_1} = 13.6 \times \frac{5}{36} \]

\[ E_{B_1} \approx 1.89\ \text{eV} \]

Ratio of energies:

\[ x = \frac{E_{L_1}}{E_{B_1}} = \frac{10.2}{1.89} \approx 5.4 \]

\[ x = 54 \times 10^{-1} \]

Hence, the required value of x = 54.

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