GATE PH 2024 • Q16 MCQ • 1 Mark

Section 9: Nuclear and Particle Physics

Nuclear & Particle Physics

Subtopic: Nuclear Models, Radioactivity & Elementary Particles

Question Statement:

Crystal structures of two metals A and B are two-dimensional square lattices with same lattice constant a. Electrons in metals behave as free electrons. The Fermi surfaces corresponding to A and B are shown by solid circles in figures. The electron concentrations in A and B are nA and nB, respectively. The value of ( nB nA ) is

Options:

  • (A) 3
  • (B) 2
  • (C) 3√3
  • (D) √2

Official Answer Key:

B

Step-by-Step Solution & Explanation

### **Official Solution & Step-by-Step Derivation (GATE PH 2024 Q.16)** **1. Theoretical Formulation & Physics Principles**: This question examines concepts in **Nuclear & Particle Physics** within *Section 9: Nuclear and Particle Physics* (1 Mark, MCQ). **2. Analytical Derivation & Formalism**: - Formulating the fundamental physics relations governing Nuclear & Particle Physics: - 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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