GATE PH 2024 • Q56 MCQ • 2 Marks

Section 1: Mathematical Physics

Mathematical Physics

Subtopic: Complex Analysis, Transforms & Differential Equations

Question Statement:

The Fourier transform and its inverse transform are respectively defined as f ̃ (𝜔) = 1 √2𝜋 ∫ f(x)ei𝜔xdx +∞ -∞ and f(x) = 1 √2𝜋 ∫ f ̃ (𝜔)e-i𝜔xd𝜔 +∞ -∞ . Consider two functions f and g. Another function f ∗ g is defined as (f ∗ g)(x) = 1 √2𝜋 ∫ f(y)g(x - y)dy +∞ -∞ Which of the following relation is/are true? Note: Tilde (~) denotes the Fourier transform.

Options:

  • (A) f ∗ g = g ∗ f
  • (B) f ∗ g̃ = g ∗ f̃
  • (C) f ∗ g̃ = fg̃
  • (D) f ∗ g̃ = f̃g̃

Official Answer Key:

B

Step-by-Step Solution & Explanation

### **Official Solution & Step-by-Step Derivation (GATE PH 2024 Q.56)** **1. Theoretical Formulation & Physics Principles**: This question examines concepts in **Mathematical Physics** within *Section 1: Mathematical Physics* (2 Marks, MCQ). **2. Analytical Derivation & Formalism**: - Formulating the fundamental physics relations governing Mathematical 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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