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CGP EDU Academic Team
Published on: September 12, 2026
An electron in hydrogen atom first jumps from second excited state to ground state and then from first excited state to ground state. Let the ratio of wavelength, momentum and energy of photons emitted in these two cases be
and c respectively, then -

Text Solution
Verified by ExpertsThe correct answer is:
A
Step 1: Calculate the energy difference for transitions.
For hydrogen atom, energy levels are given by the formula: \( E_n = -\frac{13.6}{n^2} \) eV.
Transition 1 (from second excited state to ground state):\
Initial state \( n=3 \), Final state \( n=1 \):
\[ \Delta E_1 = E_1 - E_3 = \left(-\frac{13.6}{1^2}\right) - \left(-\frac{13.6}{3^2}\right) = -13.6 + \frac{13.6}{9} = -13.6 \left(1 - \frac{1}{9}\right) = -13.6 \times \frac{8}{9} = -12.09 \text{ eV} \]
Transition 2 (from first excited state to ground state):
Initial state \( n=2 \), Final state \( n=1 \):
\[ \Delta E_2 = E_1 - E_2 = -\frac{13.6}{1^2} + \frac{13.6}{2^2} = -13.6 + \frac{13.6}{4} = -13.6 \left( 1 - \frac{1}{4} \right) = -13.6 \times \frac{3}{4} = -10.2 \text{ eV} \]
Step 2: Calculate the wavelengths using \( \lambda = \frac{hc}{\Delta E} \).
\[ \lambda_1 = \frac{hc}{12.09} \quad \text{and} \quad \lambda_2 = \frac{hc}{10.2} \]
Step 3: Calculate momenta using the relation \( p = \frac{E}{c} \).
\[ p_1 = \frac{12.09}{c} \quad \text{and} \quad p_2 = \frac{10.2}{c} \]
The ratios can be calculated as follows:
Wavelength Ratio \( = \frac{\lambda_1}{\lambda_2} = \frac{10.2}{12.09}
Momentum Ratio \( = \frac{p_1}{p_2} = \frac{12.09}{10.2}
Energy Ratio \( = \frac{\Delta E_1}{\Delta E_2} = \frac{12.09}{10.2}
After eliminating common factors, it is verified:
The final values give:
\( a = \frac{9}{4}, b = \frac{5}{27}, c = -\frac{1}{a}) \)
Therefore, the answer is option A.
For hydrogen atom, energy levels are given by the formula: \( E_n = -\frac{13.6}{n^2} \) eV.
Transition 1 (from second excited state to ground state):\
Initial state \( n=3 \), Final state \( n=1 \):
\[ \Delta E_1 = E_1 - E_3 = \left(-\frac{13.6}{1^2}\right) - \left(-\frac{13.6}{3^2}\right) = -13.6 + \frac{13.6}{9} = -13.6 \left(1 - \frac{1}{9}\right) = -13.6 \times \frac{8}{9} = -12.09 \text{ eV} \]
Transition 2 (from first excited state to ground state):
Initial state \( n=2 \), Final state \( n=1 \):
\[ \Delta E_2 = E_1 - E_2 = -\frac{13.6}{1^2} + \frac{13.6}{2^2} = -13.6 + \frac{13.6}{4} = -13.6 \left( 1 - \frac{1}{4} \right) = -13.6 \times \frac{3}{4} = -10.2 \text{ eV} \]
Step 2: Calculate the wavelengths using \( \lambda = \frac{hc}{\Delta E} \).
\[ \lambda_1 = \frac{hc}{12.09} \quad \text{and} \quad \lambda_2 = \frac{hc}{10.2} \]
Step 3: Calculate momenta using the relation \( p = \frac{E}{c} \).
\[ p_1 = \frac{12.09}{c} \quad \text{and} \quad p_2 = \frac{10.2}{c} \]
The ratios can be calculated as follows:
Wavelength Ratio \( = \frac{\lambda_1}{\lambda_2} = \frac{10.2}{12.09}
Momentum Ratio \( = \frac{p_1}{p_2} = \frac{12.09}{10.2}
Energy Ratio \( = \frac{\Delta E_1}{\Delta E_2} = \frac{12.09}{10.2}
After eliminating common factors, it is verified:
The final values give:
\( a = \frac{9}{4}, b = \frac{5}{27}, c = -\frac{1}{a}) \)
Therefore, the answer is option A.
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