# Electromagnetic Waves Properties > Transverse nature, E0/B0 = c, energy and momentum of EM waves with the spectrum order for NEET Physics revision. - Canonical URL: https://prepelephant.com/topics/neet-ug/physics/em-waves-properties-neet - Exam / course: NEET-UG · Subject: Physics - Publisher: PrepElephant (https://prepelephant.com) — Prepared and reviewed by the PrepElephant Academic Review Team - First published: 2026-10-02 - Last updated: 2026-10-02 - How to cite: "Electromagnetic Waves Properties", PrepElephant, https://prepelephant.com/topics/neet-ug/physics/em-waves-properties-neet ## Direct answer Light, radio signals, X-rays and gamma rays form one family: electromagnetic waves in which the electric and magnetic fields oscillate perpendicular to each other and to the direction of travel (transverse), moving in vacuum at c = 1/√(μ0ε0) = 3 × 10^8 m/s. The two field amplitudes are locked in a fixed ratio, E0/B0 = c, and the wave carries both energy and momentum — an absorbing surface feels radiation pressure. Frequency and wavelength connect through c = νλ. The spectrum in order of increasing frequency runs radio, microwaves, infrared, visible, ultraviolet, X-rays and gamma rays, with accelerated charges as the universal source and each band having its own production and detection story in NCERT's table. ## What you must remember - **Transverse geometry:** E ⊥ B ⊥ direction of propagation; the fields oscillate in phase, peaking and vanishing together. - **Fixed amplitude ratio:** E0/B0 = c = 3 × 10^8 m/s; equivalently B0 = E0/c, so magnetic amplitudes are tiny in tesla. - **Speed from constants:** c = 1/√(μ0ε0) in vacuum, derived from Maxwell's equations; in a medium v = 1/√(με) = c/n. - **Energy and intensity:** energy density is shared equally between the fields; intensity of a sinusoidal wave I = ½ ε0 E0² c. - **Momentum and pressure:** a wave carrying energy U has momentum U/c; pressure on a perfect absorber is I/c, on a perfect reflector 2I/c. - **Spectrum order (increasing frequency):** radio → microwaves → infrared → visible (about 400-700 nm) → ultraviolet → X-rays → gamma rays; NEET asks the ordering more than anything numerical here. - **Production logic:** oscillating or accelerated charges radiate — radio from antennas and LC circuits, IR from hot bodies and molecular vibrations, X-rays from fast electrons striking a metal target, gamma rays from nuclei. ## Numbers worth knowing Run a wave with E0 = 60 V/m. The companion field is B0 = E0/c = 60/(3 × 10^8) = 2 × 10^-7 T — small, because the ratio itself is an enormous speed. The intensity works out to I = ½ × (8.85 × 10^-12) × 60² × (3 × 10^8) ≈ 4.8 W/m², the kind of two-step substitution NEET expects you to do in thirty seconds. Flip the logic for identification problems: a 150 m radio wave carries ν = c/λ = 2 MHz, placing it firmly in the radio band, while a 10^-12 m wave is gamma ray territory. The skill being tested is unit hygiene — E in V/m, B in tesla, λ in metres — and remembering which field amplitude gets divided by c, since the options include the answer inverted by a factor of 10^8. ## Where NEET sets the trap Chapter 8's spectrum table (wavelength range, production method, detector) is the direct source of most statements. The recurring confusions: microwaves versus infrared (microwaves are longer in wavelength, produced by special vacuum tubes such as klystrons and magnetrons per NCERT, not by hot filaments); ultraviolet as the first ionising band; and the claim that all EM waves travel at c only in vacuum — in matter they slow by the refractive index, which is optics meeting Maxwell. Assertion-reason staples: EM waves need no medium; the fields mutually regenerate so neither is "caused first"; and radiation pressure exists even though photons are massless. A student who can walk the spectrum with a production story for each band handles nearly every question this chapter offers. ## Frequently asked questions ### Are the electric and magnetic fields of an EM wave in phase? Yes; E and B peak together, remain mutually perpendicular, and both stay perpendicular to the direction of propagation — pure transverse character. ### What is the ratio of field amplitudes in an electromagnetic wave? E0/B0 = c, the speed of light — about 3 × 10^8 m/s in vacuum; dividing the wrong way is the classic error the options are built around. ### Which part of the spectrum arises from nuclear processes? Gamma rays, emitted by radioactive nuclei; X-rays, by contrast, come from high-energy electronic transitions when fast electrons strike a metal target. ### Do electromagnetic waves carry momentum? Yes; a wave of energy U carries momentum U/c, producing radiation pressure I/c on a perfect absorber and twice that on a perfect reflector. ### Which radiation has wavelength just shorter than visible light? Ultraviolet, roughly 400 nm downward — ionising, invisible, and responsible for sunburn and ozone chemistry.