Question

Ionisation energy of H-atom is \(13.6 \text{ eV}\). The wavelength of the spectral line emitted when an electron in \(\text{Be}^{3+}\) comes from \(5^{\text{th}}\) energy level to \(2^{\text{nd}}\) energy level is:

• A. \(43.5 \text{ nm}\)
• B. \(4350 \text{ nm}\)
• C. \(4.35 \text{ nm}\)
• D. \(435 \text{ nm}\)

Hint:

For hydrogen-like ions, wavelength decreases rapidly with increasing atomic number because: \[ \lambda \propto \frac{1}{Z^2} \] Thus, transitions in ions like \(\text{He}^+\), \(\text{Li}^{2+}\), and \(\text{Be}^{3+}\) occur in much shorter wavelength regions compared to hydrogen.

Answer 1

The Correct Option is A