Electromagnetic Waves JEE Main previous year questions with solutions

4 solved JEE Main questions on Electromagnetic Waves, free to read — no sign-in needed. The full chapter has 172 questions; sign in to attempt the remaining 168 in the exam simulator.

Answers checked against the official answer keys.

1. Q1JEE Main 2026 (08 Apr, Shift 2)Electromagnetic Spectrum
   A monochromatic source of light operating at $15$ kW emits $2.5\times 10^{22}$ photons/s. The region of an electromagnetic spectrum to which the emitted electromagnetic radiation belongs to ________. (Take $h=6.6\times 10^{-34}$ J·s and $c=3\times 10^8$ m/s).
   1. A.Microwave
   2. B.Infrared
   3. C.Visible
   4. D.Ultraviolet
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   Answer: (D)

   Power of the source, $P = 15 \text{ kW} = 15 \times 10^3 \text{ J/s}$ Number of photons emitted per second, $n = 2.5 \times 10^{22} \text{ s}^{-1}$ Energy of one photon, $E = \dfrac{P}{n} = \dfrac{15 \times 10^3}{2.5 \times 10^{22}} = 6 \times 10^{-19} \text{ J}$ Using $E = \dfrac{hc}{\lambda}$, we get $\lambda = \dfrac{hc}{E}$ $\lambda = \dfrac{6.6 \times 10^{-34} \times 3 \times 10^8}{6 \times 10^{-19}} = 3.3 \times 10^{-7} \text{ m} = 330 \text{ nm}$ The wavelength $330 \text{ nm}$ lies in the ultraviolet region of the electromagnetic spectrum. Answer: Ultraviolet
2. Q2JEE Main 2025 (29 Jan, Shift 1)Electromagnetic Waves and Maxwell's equations
   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 ($\mathbf{R}$): 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.Both (A) and (R) are true and (R) is the correct explanation of $(\mathbf{A})$
   2. B.Both $(\mathbf{A})$ and $(\mathbf{R})$ are true but $(\mathbf{R})$ is not the correct explanation of $(\mathbf{A})$
   3. C.(A) is false but (R) is true
   4. D.(A) is true but ($\mathbf{R}$) is false
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   Answer: (C)

   EM wave carry both energy and momentum. Rest mass of photon is zero.
3. Q3JEE Main 2023 (11 Apr, Shift 1)Force and Energy stored in capacitor
   The electric field in an electromagnetic wave is given as $\vec{E}=20\sin \omega \left(t-\dfrac{x}{c}\right)\vec{j}N{C}^{-1}$, where $\omega$ and $c$ are angular frequency and velocity of electromagnetic wave respectively. The energy contained in a volume of $5\times {10}^{-4}{m}^{3}$ will be (Given ${\epsilon }_{0}=8.85\times {10}^{-12}{C}^{2}{N}^{-1}{m}^{-2}$)
   1. A.$88.5\times {10}^{-13}J$
   2. B.$17.7\times {10}^{-13}J$
   3. C.$28.5\times {10}^{-13}J$
   4. D.$8.85\times {10}^{-13}J$
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   Answer: (D)

   Given that, $\vec{E}=20\sin \omega \left(t-\dfrac{x}{c}\right)\vec{j}N{C}^{-1}$ The average energy density of an electromagnetic wave is $\dfrac{1}{2}{\epsilon }_{0}{{E}^{2}}_{0}$. The total energy stored is ${E}_{\text{total}}=\dfrac{1}{2}{\epsilon }_{0}{E}_{0}^{2}\times volume$ $\Rightarrow {E}_{total}=\dfrac{1}{2}\times 8.85\times {10}^{-12}\times (20{)}^{2}\times 5\times {10}^{-4} =8.85\times {10}^{-13}J$
4. Q4JEE Main 2022 (28 Jun, Shift 1)Beats
   A radar sends an electromagnetic signal of electric field $\left({E}_{0}\right)=2.25V{m}^{-1}$ and magnetic field $\left({B}_{0}\right)=1.5\times {10}^{-8}T$ which strikes a target on line of sight at a distance of $3km$ in a medium. After that, a part of signal (echo) reflects back towards the radar with same velocity and by same path. If the signal was transmitted at time $t=0$ from radar, then after how much time echo will reach to the radar?
   1. A.$2.0\times {10}^{-5}s$
   2. B.$4.0\times {10}^{-5}s$
   3. C.$1.0\times {10}^{-5}s$
   4. D.$8.0\times {10}^{-5}s$
   Show answer & solution

   Answer: (B)

   The speed of light is given by, $c=\dfrac{{E}_{0}}{{B}_{0}}=\dfrac{2.25}{1.5\times {10}^{-8}}=1.5\times {10}^{8}{ms}^{-1}$ Therefore, time taken for the echo will be, $t=\dfrac{2d}{c}=\dfrac{6\times {10}^{3}}{1.5\times {10}^{8}}=4\times {10}^{-5}s$