Question:medium

A particular hydrogen like ion emits radiation of frequency $2.92 \times 10^{15}$ Hz when it makes transition from n=3 to n=1. The frequency in Hz of radiation emitted in transition from n=2 to n=1 will be :

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For frequency ratios, you don't need the value of $Z$ or Rydberg's constant. Simply use the term $(1/n_1^2 - 1/n_2^2)$.
Updated On: Feb 19, 2026
  • $4.38 \times 10^{15}$
  • $6.57 \times 10^{15}$
  • $0.44 \times 10^{15}$
  • $2.46 \times 10^{15}$
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The Correct Option is D

Solution and Explanation

To determine the frequency of the radiation emitted when the electron transitions from \( n=2 \) to \( n=1 \) for a hydrogen-like ion, we can use the Rydberg formula for the frequency of emitted radiation:

v = RZ^2\left(\frac{1}{n_1^2} - \frac{1}{n_2^2}\right)

where:

  • \( v \) is the frequency of radiation emitted.
  • \( R \) is the Rydberg constant (\( R = 3.29 \times 10^{15} \) Hz for hydrogen atom).
  • \( Z \) is the atomic number of the atom/ion.
  • \( n_1 \) and \( n_2 \) are the principal quantum numbers of the initial and final states.

Given that the transition from \( n=3 \) to \( n=1 \) has a frequency of \( 2.92 \times 10^{15} \) Hz, we can write this equation as:

2.92 \times 10^{15} = RZ^2\left(\frac{1}{1^2} - \frac{1}{3^2}\right)

Simplifying:

2.92 \times 10^{15} = RZ^2\left(1 - \frac{1}{9}\right) = RZ^2\left(\frac{8}{9}\right)

We need to find the frequency for the transition from \( n=2 \) to \( n=1 \):

v = RZ^2\left(\frac{1}{1^2} - \frac{1}{2^2}\right) = RZ^2\left(1 - \frac{1}{4}\right) = RZ^2\left(\frac{3}{4}\right)

Dividing the two expressions:

\frac{v}{2.92 \times 10^{15}} = \frac{\left(\frac{3}{4}\right)}{\left(\frac{8}{9}\right)}

This simplifies to:

v = 2.92 \times 10^{15} \times \frac{3}{4} \times \frac{9}{8}

Simplifying the calculation:

v = 2.92 \times 10^{15} \times \frac{27}{32}

Calculating the value:

v = \frac{78.84}{32} \times 10^{15} = 2.46 \times 10^{15} \text{ Hz}

Therefore, the frequency of the radiation emitted when transitioning from \( n=2 \) to \( n=1 \) is \( 2.46 \times 10^{15} \) Hz. The correct answer is $2.46 \times 10^{15}$.

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