Electromagnetic Wave - NEET Previous Year Questions with Complete Solutions

Gamma rays have the highest frequency (greater than 10¹⁸ Hz) and the shortest wavelength (less than 0.01 nm) in the electromagnetic spectrum. They are produced by radioactive nuclei and nuclear reactions. In NEET, gamma rays are associated with cancer treatment (radiotherapy) and the sterilisation of surgical instruments.

Displacement current (I_d = ε₀ dΦ_E/dt) was introduced by Maxwell to resolve the inconsistency in Ampere's Circuital Law when applied to a charging capacitor. NEET asks about it almost every two years — either as a direct formula question or as a conceptual question about why Maxwell modified Ampere's law. Understanding the capacitor-charging scenario is enough to answer any NEET question on this topic

NTA typically asks 1 to 2 questions from Electromagnetic Waves in NEET-UG every year. Based on PYQ analysis from 2010–2024, the average is approximately 1.4 questions per year, contributing 4–8 marks. The chapter is short and high-scoring, making it one of the best chapters for last-minute revision before the exam.

In an electromagnetic wave, the amplitudes of the electric field (E₀) and magnetic field (B₀) are related by: E₀/B₀ = c, where c is the speed of light in vacuum (3 × 10⁸ m/s). Both fields are always in phase — they reach their maximum and minimum values at exactly the same points in space and time.

Yes, all electromagnetic waves are transverse. The electric field (E) and magnetic field (B) vectors oscillate perpendicular to each other and to the direction of wave propagation. This transverse nature is a frequently tested fact in NEET. It also means EM waves can be polarised — unlike longitudinal waves such as sound.

All electromagnetic waves — regardless of frequency or wavelength — travel at the speed of light in vacuum: c = 3 × 10⁸ m/s. This value is derived from Maxwell's equations as c = 1/√(μ₀ε₀). In a medium, the speed reduces to v = c/n, where n is the refractive index of the medium.