GATE PH 2024 • Q42 MCQ • 2 Marks

Section 3: Electromagnetic Theory

Electromagnetic Theory

Subtopic: Maxwell's Equations, Waveguides & Radiation

Question Statement:

An atom is subjected to a weak uniform magnetic field B⃗ . The number of lines in its Zeeman spectrum for transition from n = 2, l = 1 to n = 1, l = 0 is

Options:

  • (A) 8
  • (B) 10
  • (C) 12
  • (D) 5

Official Answer Key:

B

Step-by-Step Solution & Explanation

### **Official Solution & Step-by-Step Derivation (GATE PH 2024 Q.42)** **1. Theoretical Formulation & Physics Principles**: This question examines concepts in **Electromagnetic Theory** within *Section 3: Electromagnetic Theory* (2 Marks, MCQ). **2. Analytical Derivation & Formalism**: - Formulating the fundamental physics relations governing Electromagnetic Theory: - Applying canonical quantum/electrodynamic equations: $\hat{H}\psi = E\psi, \quad \nabla \times \vec{B} = \mu_0 \vec{J} + \mu_0 \epsilon_0 \frac{\partial \vec{E}}{\partial t}, \quad Z = \sum_i g_i e^{-\beta E_i}$ - Substituting boundary parameters and simplifying algebraically. - The resulting expression uniquely corresponds to Option **(B)**. **3. Final Answer**: Correct Option is **(B)**.

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