The electric field of an electromagnetic wave travelling through a medium is given by vec E (x, t)=25 sin (2.0 × 10 15 t-10 7 x ) hat n then the refractive index of the medium is \ \ \ \ 。 (All given measurement are in SI units)

Physics · Electromagnetic Waves

JEE Main 2026 — 28 January, Morning Shift — Question 29

The electric field of an electromagnetic wave travelling through a medium is given by $\vec{E}(x, t)=25 \sin \left(2.0 \times 10^{15} t-10^{7} x\right) \hat{n}$ then the refractive index of the medium is $\_\_\_\_$ 。 (All given measurement are in SI units)

Option A:
1.2
Option B:
2
Option C:
1.5
Correct
Option D:
1.7

Answer: C

Step-by-step solution

$\omega=2 \times 10^{15} \mathrm{rad} / \mathrm{s}$ $\mathrm{k}=10^{7} \mathrm{~m}^{-1}$ $\mathrm{V}=\frac{2 \pi}{\mathrm{k}} \cdot \frac{\omega}{2 \pi}=\frac{\omega}{\mathrm{k}}=\frac{2 \times 10^{15}}{10^{7}}=2 \times 10^{8}=\frac{\mathrm{C}}{1.5}$ $\Rightarrow \mu=1.5$

Answer key and solution verified before publishing.

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Exam: JEE Main 2026
Paper: 28 January, Morning Shift
Subject: Physics
Chapter: Electromagnetic Waves
Topic: Properties of EM Waves and Electromagnetic Spectrum