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JEE Main 2025 January Physics: Electromagnetic Waves – Previous Year Questions

All 10 questions asked from Electromagnetic Waves in JEE Main 2025 January Physics (22, 23, 24, 28 and 29 January, all shifts). This chapter is about 4.0% of the 250 Physics questions in the session: 7 single-correct (MCQ) and 3 numerical-value questions. Select an answer to attempt each question, and open “View solution” under it.

10questions
7MCQ
3numerical
4.0%of Physics paper

Topics asked in this chapter

  • Displacement Current – 2 questions
  • EM Waves & Spectrum – 8 questions

Displacement Current

Q122 Jan 2025 · Shift 2Numerical
A parallel plate capacitor of area $A = 16\ \mathrm{cm^2}$ and separation between the plates 10 cm, is charged by a DC current. Consider a hypothetical plane surface of area $A_0 = 3.2\ \mathrm{cm^2}$ inside the capacitor and parallel to the plates. At an instant, the current through the circuit is 6 A. At the same instant the displacement current through $A_0$ is mA.
Q223 Jan 2025 · Shift 2Numerical
A time varying potential difference is applied between the plates of a parallel plate capacitor of capacitance 2.5 $\mu$F. The dielectric constant of the medium between the capacitor plates is 1. It produces an instantaneous displacement current of 0.25 mA in the intervening space between the capacitor plates, the magnitude of the rate of change of the potential difference will be Vs$^{-1}$.

EM Waves & Spectrum

Q323 Jan 2025 · Shift 1MCQ
The electric field of an electromagnetic wave in free space is $\vec{E} = 57\cos\left[7.5\times10^{6}t - 5\times10^{-3}(3x+4y)\right](4\hat{i} - 3\hat{j})$ N/C. The associated magnetic field in Tesla is
  1. A
    $\vec{B} = -\frac{57}{3\times10^{8}}\cos\left[7.5\times10^{6}t - 5\times10^{-3}(3x+4y)\right](5\hat{k})$
  2. B
    $\vec{B} = \frac{57}{3\times10^{8}}\cos\left[7.5\times10^{6}t - 5\times10^{-3}(3x+4y)\right](5\hat{k})$
  3. C
    $\vec{B} = -\frac{57}{3\times10^{8}}\cos\left[7.5\times10^{6}t - 5\times10^{-3}(3x+4y)\right](\hat{k})$
  4. D
    $\vec{B} = \frac{57}{3\times10^{8}}\cos\left[7.5\times10^{6}t - 5\times10^{-3}(3x+4y)\right](\hat{k})$
Q423 Jan 2025 · Shift 2MCQ
A plane electromagnetic wave of frequency 20 MHz travels in free space along the $+x$ direction. At a particular point in space and time, the electric field vector of the wave is $E_y = 9.3\ \mathrm{Vm^{-1}}$. Then, the magnetic field vector of the wave at that point is
  1. A
    $B_z = 3.1\times10^{-8}$ T
  2. B
    $B_z = 1.55\times10^{-8}$ T
  3. C
    $B_z = 9.3\times10^{-8}$ T
  4. D
    $B_z = 6.2\times10^{-8}$ T
Q524 Jan 2025 · Shift 2MCQ
Arrange the following in the ascending order of wavelength ($\lambda$) :
(A) Microwaves ($\lambda_1$) (B) Ultraviolet rays ($\lambda_2$) (C) Infrared rays ($\lambda_3$) (D) X-rays ($\lambda_4$)
Choose the most appropriate answer from the options given below :
  1. A
    $\lambda_4<\lambda_3<\lambda_2<\lambda_1$
  2. B
    $\lambda_4<\lambda_2<\lambda_3<\lambda_1$
  3. C
    $\lambda_3<\lambda_4<\lambda_2<\lambda_1$
  4. D
    $\lambda_4<\lambda_3<\lambda_1<\lambda_2$
Q628 Jan 2025 · Shift 1MCQ
Due to presence of an em-wave whose electric component is given by $E = 100\sin(\omega t - kx)\ \mathrm{NC^{-1}}$, a cylinder of length 200 cm holds certain amount of em-energy inside it. If another cylinder of same length but half diameter than previous one holds same amount of em-energy, the magnitude of the electric field of the corresponding em-wave should be modified as
  1. A
    $50\sin(\omega t-kx)\ \mathrm{NC^{-1}}$
  2. B
    $200\sin(\omega t-kx)\ \mathrm{NC^{-1}}$
  3. C
    $400\sin(\omega t-kx)\ \mathrm{NC^{-1}}$
  4. D
    $25\sin(\omega t-kx)\ \mathrm{NC^{-1}}$
Q728 Jan 2025 · Shift 2MCQ
The magnetic field of an E.M. wave is given by $\vec{B} = \left(\frac{\sqrt{3}}{2}\hat{i} + \frac{1}{2}\hat{j}\right)30\sin\left[\omega\left(t - \frac{z}{c}\right)\right]$ (S.I. Units). The corresponding electric field in S.I. units is :
  1. A
    $\vec{E} = \left(\frac{1}{2}\hat{i} + \frac{\sqrt{3}}{2}\hat{j}\right)30c\sin\left[\omega\left(t + \frac{z}{c}\right)\right]$
  2. B
    $\vec{E} = \left(\frac{\sqrt{3}}{2}\hat{i} - \frac{1}{2}\hat{j}\right)30c\sin\left[\omega\left(t + \frac{z}{c}\right)\right]$
  3. C
    $\vec{E} = \left(\frac{3}{4}\hat{i} + \frac{1}{4}\hat{j}\right)30c\cos\left[\omega\left(t - \frac{z}{c}\right)\right]$
  4. D
    $\vec{E} = \left(\frac{1}{2}\hat{i} - \frac{\sqrt{3}}{2}\hat{j}\right)30c\sin\left[\omega\left(t - \frac{z}{c}\right)\right]$
Q829 Jan 2025 · Shift 1MCQ
Given below are two statements : one is labelled as Assertion (A) and the other is labelled as Reason (R).
Assertion (A) : Electromagnetic waves carry energy but not momentum.
Reason (R) : Mass of a photon is zero.
In the light of the above statements, choose the most appropriate answer from the options given below :
  1. A
    (A) is true but (R) is false
  2. B
    (A) is false but (R) is true
  3. C
    Both (A) and (R) are true and (R) is the correct explanation of (A)
  4. D
    Both (A) and (R) are true but (R) is not the correct explanation of (A)
Q929 Jan 2025 · Shift 2MCQ
A plane electromagnetic wave propagates along the $+x$ direction in free space. The components of the electric field, $\vec{E}$ and magnetic field, $\vec{B}$ vectors associated with the wave in Cartesian frame are
  1. A
    $E_y,\ B_x$
  2. B
    $E_z,\ B_y$
  3. C
    $E_y,\ B_z$
  4. D
    $E_x,\ B_y$
Q1029 Jan 2025 · Shift 2Numerical
A parallel plate capacitor consisting of two circular plates of radius 10 cm is being charged by a constant current of 0.15 A. If the rate of change of potential difference between the plates is $7\times10^{8}$ V/s then the integer value of the distance between the parallel plates is (Take, $\epsilon_0 = 9\times10^{-12}\ \frac{\mathrm{F}}{\mathrm{m}}$, $\pi = \frac{22}{7}$) $\mu$m.
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