Electromagnetic Waves Quiz – JEE Main 2026 | EM Waves PYQs

Electromagnetic Waves – JEE Main 2026 Quiz

10 Questions | MCQ + Numerical | With Theory

Q1. A radar signal strikes a target at a distance of 3 km and returns back with same speed. Time taken for echo to reach radar (in μs) is:
Correct Answer: 20
Q2. If an EM wave stores same energy in two cylinders of same length but second has half the diameter, the electric field amplitude should be:
Q3. A capacitor of area 16 cm² is charged by a current of 6 A. Displacement current through area 3.2 cm² (in mA) is:
Correct Answer: 1200
Q4. If electric field of an EM wave is E = 300 sin(5π×10³x − 3π×10¹¹t) V/m, magnetic field amplitude is:
Q5. If magnetic field amplitude is 6 × 10⁻⁷ T, maximum electric field is:
Q6. Correct relation between E₀ and B₀ of an EM wave is:
Q7. Sunlight exerts force 7.2×10⁻⁹ N on area 36 cm². Energy flux (W/cm²) is:
Q8. Average force on non-reflecting surface is 2.4×10⁻⁴ N. Energy flux is 360 W/cm². Area of surface is:
Q9. Displacement current is 4.425 μA when dV/dt = 10⁶ V/s. Distance between plates is x×10⁻³ m. Find x.
Correct Answer: 8
Q10. Speed of light in a medium is 0.2c. Ratio of relative permittivity to refractive index is x : 1. Find x.
Correct Answer: 5

Electromagnetic Waves – Quick Theory

Electromagnetic waves are transverse waves consisting of oscillating electric and magnetic fields which are perpendicular to each other and also perpendicular to the direction of propagation.

  • EM waves do not require a medium and can propagate in vacuum.
  • Speed of EM waves in vacuum: c = 3 × 10⁸ m/s.
  • Relation between electric and magnetic field: E = cB
  • Energy is equally distributed between electric and magnetic fields.
  • Displacement current arises due to time-varying electric field and is given by:
    Id = ε₀ (dΦE/dt)
  • Radiation pressure for complete absorption:
    P = I / c
  • EM spectrum includes radio waves, microwaves, infrared, visible light, ultraviolet, X-rays and gamma rays.

This chapter is important for JEE Main numerical and assertion-based questions.

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