Electromagnetic Waves

JEE Main level, single correct, medium

93 of 165

Question 93 of 165

The electric field of a plane electromagnetic wave propagating along the x direction in vacuum is E⃗=E0jcos(ωt−kx).\vec{E}={E}_{0}jcos(\omega t-kx). The magnetic field B⃗,\vec{B}, at the moment t=0t=0 is:

Show answer and solution

Answer: (C) B⃗=E0μ0ϵ0cos⁡(kx)k^\vec{B}={E}_{0}\sqrt{{\mu }_{0}{\epsilon }_{0}}\cos (kx)\hat{k}

B0=E0C=E01/μ0ϵ0=E0μ0ϵ0{B}_{0}=\dfrac{{E}_{0}}{C}=\dfrac{{E}_{0}}{1/\sqrt{{\mu }_{0}{\epsilon }_{0}}}={E}_{0}\sqrt{{\mu }_{0}{\epsilon }_{0}}
As the light is propagating in xx direction
and E^×B^∣∣C^\hat{E}\times \hat{B}||\hat{C}
∴∴ B⃗\vec{B} should be in K^\hat{K} direction

JEE Main question paper PDF

Open a shift to read the full paper on this page, or download it.

JEE Main 2025 Apr 2 Shift 1 question paper

Open Download PDF

Opening paper…

Explain it as a whiteboard videoStep-by-step, in Hinglish or English. Your first video needs no login.Solved it on paper but got it wrong?Upload a photo of your working. Mistake Doctor marks the exact line that broke.

More Physics practice

JEE Main Physics practice question on Electromagnetic Waves (Electromagnetic Waves and Maxwell's equations), with the answer and a step-by-step solution. Scan a question from your own book or paper to get a whiteboard video.