Physics · Electromagnetic Waves · NEET
Radio waves: electrons oscillating in an antenna or LC circuit. Microwaves: special vacuum tubes called klystron or magnetron valves. Infrared: vibration of atoms and molecules (hot bodies). Visible light: electron transitions between energy levels in atoms. Ultraviolet: high-energy electron transitions in atoms (very hot bodies, arcs, the Sun). X-rays: fast electrons suddenly stopped by a heavy metal target. Gamma rays: from the nucleus during radioactive decay (nuclear transitions). One rule underneath all of them: an accelerating charge radiates. This exact matching was asked in NEET 2026, so learn the pairs.
They differ by their SOURCE, not just energy. X-rays are made when fast-moving electrons hit a metal target and decelerate suddenly (outside the nucleus, from the electron cloud region). Gamma rays are emitted by the NUCLEUS itself when it drops to a lower energy state during radioactive decay. NEET loves this trap: if the question says 'nuclear origin' or 'radioactive decay', the answer is gamma rays, even if the energy sounds like X-rays.
From electrons. Visible light (and UV) is produced when an electron jumps from a higher energy level to a lower energy level inside an atom — this is an electron transition. The nucleus is not involved. Only gamma rays come from the nucleus. Keep this line: electron jumps give visible/UV, nuclear jumps give gamma.
Both do. Klystron valves and magnetron valves are special vacuum tubes used to generate microwaves (a magnetron is what sits inside your microwave oven). In NEET matching questions, 'klystron or magnetron valve' is the standard production clue for MICROWAVES. Radio waves, by contrast, come from oscillating electrons in an antenna/LC circuit — not from these valves.
A stationary charge gives only a static electric field, and a charge moving at constant velocity gives only a steady magnetic field — neither radiates. Only when a charge accelerates (changes speed or direction) do you get a time-varying E field, which makes a time-varying B field, which regenerates E, and so on. This self-sustaining pair is the EM wave. Every source above (oscillating antenna electrons, vibrating molecules, jumping electrons, stopping electrons, decaying nuclei) is just a different way of making a charge accelerate.
Match List I (Electromagnetic wave) with List II (Production): (A) Microwave (B) Visible light (C) Gamma rays (D) Infrared, with (I) Electron transitions in atoms (II) Radioactive decay / nuclear transitions (III) Vibration of atoms and molecules (IV) Klystron or magnetron valve. Choose the correct match.
Out of the following options, which one can be used to produce a propagating electromagnetic wave?
Try the real previous-year questions from this chapter — each with the answer and a full solution.
An accelerating charge always radiates an EM wave. Every specific source — oscillating antenna electrons, vibrating molecules, jumping atomic electrons, decelerating electrons, decaying nuclei — is just a different way of accelerating a charge.
Only gamma rays. They are emitted by the nucleus during radioactive decay (nuclear transitions). All other EM waves are produced outside the nucleus.
Radio waves come from electrons oscillating in an antenna or LC circuit. Microwaves come from special vacuum tubes — klystron or magnetron valves.
By bombarding a heavy metal target with fast-moving electrons. The electrons decelerate suddenly, and this rapid acceleration of charge emits X-rays.
Visible light and ultraviolet rays. When an electron jumps from a higher energy level to a lower one inside an atom, it emits a photon in the visible or UV band.
