Class JEE Physics ALL Q #1182
COMPETENCY BASED
APPLY
4 Marks 2026 JEE Main 2026 (Online) 21st January Morning Shift MCQ SINGLE
A wave propagates whose electric field is given by $\vec{E}=69~\sin(\omega t-kx)\hat{j}$. Find the direction of the magnetic field.
(A) $\hat{k}$
(B) $-\hat{k}$
(C) $\frac{\hat{i}+\hat{j}}{\sqrt{2}}$
(D) $\frac{\hat{i}-\hat{j}}{\sqrt{2}}$
Prev Next

AI Tutor Explanation

Powered by Gemini

Step-by-Step Solution

  1. The direction of propagation of the wave is given by the direction of $\vec{E} \times \vec{B}$.
  2. The electric field is along the $\hat{j}$ direction, and the wave propagates along the $\hat{i}$ direction (from the term $kx$ in the argument of the sine function).
  3. Therefore, $\hat{i} = \hat{j} \times \hat{B}$.
  4. To satisfy this equation, $\hat{B}$ must be in the $-\hat{k}$ direction, since $\hat{j} \times (-\hat{k}) = \hat{i}$.

Correct Answer: B

|
AI Suggestion: Option B

AI generated content. Review strictly for academic accuracy.

Pedagogical Audit
Bloom's Analysis: This is an APPLY question because it requires applying the relationship between the directions of electric field, magnetic field, and wave propagation.
Knowledge Dimension: PROCEDURAL
Justification: The question requires applying a known procedure (right-hand rule or the relationship between E, B, and the direction of propagation) to determine the direction of the magnetic field.
Syllabus Audit: In the context of JEE, this is classified as COMPETENCY. It tests the student's ability to apply the concepts of electromagnetic waves to determine the direction of the magnetic field, which is a competency-based application.

More from this Chapter

MCQ_SINGLE
Find the volume flow rate in the Venturi meter shown below in which water is flowing. Given $\frac{A}{a}=2$, $A=\sqrt{3}m^{2}$, difference in levels is 5 cm and $\rho=1000~kg~m^{-3}$.
MCQ_SINGLE
If the electric field of an EM wave is given by $60[\sin(3\times10^{14}t)+\sin(12\times10^{14}t)]$ at $x=0$ and it falls on a photosensitive material having work function $2.8 eV$, find the maximum kinetic energy (in eV) of the ejected electrons.
MCQ_SINGLE
In series R-L circuit, voltage of battery is $10~V$. Resistance and inductance are $10~\Omega$ and $10~mH$ respectively. Find energy stored in the inductor when current reaches $\frac{1}{e}$ times of maximum value :
MCQ_SINGLE
Two disc having same moment of inertia about their axis. Thickness is $t_{1}$ and $t_{2}$ and they have same density. If $R_{1}/R_{2}=1/2$, then find $t_{1}/t_{2}$ :
MCQ_SINGLE
An ideal solenoid is kept with its axis vertical. A current $I_{0}$ is flowing in the solenoid. A charge q is thrown vertically downward inside the solenoid. The acceleration of the charged particle is:
View All Questions