Electromagnetic Waves — NEET Physics MCQs with answers

Electromagnetic Waves is a Class 12 Physics chapter in the NEET (UG) syllabus. NEET720 has 451 reviewed practice questions on it, each with a quick answer and a step-by-step explanation. The 8 questions below are free and fixed, so you can bookmark this page; the full chapter, plus mistake tracking and spaced revision, is in the app.

Topics covered

EM wave characteristics · Displacement current and Maxwell's contribution · Properties of EM waves · EM spectrum and applications · Electromagnetic Waves · EM wave relations · Momentum of EM waves · Maxwell's Equations · Electromagnetic Spectrum · Speed of EM waves · Nature of EM waves · Wave nature · EM wave field amplitudes · Poynting vector · Displacement current · Wave properties · Energy in EM waves · EM spectrum · Intensity · Radiation pressure · Microwaves · Detection of EM waves · Uses of EM waves · EM wave energy · EM wave in medium · X-rays · EM wave propagation · EM Wave Properties

8 free Electromagnetic Waves practice questions with answers

Choose an answer in your head before opening it. Each explanation says why the correct option is right and, where relevant, why the tempting wrong option is wrong.

1. Question 1 · medium · Properties of EM waves

   Electromagnetic waves are produced by:

   • A.accelerated (or oscillating) electric charges
   • B.charges moving with constant velocity only
   • C.stationary point charges with large magnitude
   • D.any current-carrying conductor irrespective of whether the current is steady or changing
   Show answer and explanation

   Answer: A. accelerated (or oscillating) electric charges

   Only accelerating charges (oscillating currents) radiate electromagnetic waves; static or uniformly moving charges do not.

   An EM wave is generated whenever a charge accelerates, since the associated changing electric and magnetic fields propagate outward and regenerate each other via Maxwell's equations. A charge at rest gives a static E field; a charge in uniform velocity gives fields that move with it but do not radiate energy away. Only acceleration (as in an oscillating charge/current in an antenna) produces genuine outward-radiating EM waves.

   Common mistake: Believing any current, even steady DC, produces EM waves.

2. Question 2 · hard · Properties of EM waves

   Unpolarised light and plane-polarised light both consist of transverse electromagnetic waves. The essential physical difference between them is that:

   • A.in polarised light the electric field vibrates along one fixed direction perpendicular to propagation, while in unpolarised light it changes direction randomly and rapidly in the transverse plane
   • B.polarised light has E purely transverse while unpolarised light has some longitudinal E component
   • C.unpolarised light has no magnetic field component, only polarised light does
   • D.polarised light travels slower than unpolarised light in the same medium
   Show answer and explanation

   Answer: A. in polarised light the electric field vibrates along one fixed direction perpendicular to propagation, while in unpolarised light it changes direction randomly and rapidly in the transverse plane

   Polarisation refers only to whether the transverse E-field direction is fixed (polarised) or randomly varying (unpolarised); both remain fully transverse EM waves with accompanying B fields.

   Both polarised and unpolarised light are transverse EM waves with E and B perpendicular to each other and to the propagation direction. In unpolarised light (e.g. from an ordinary bulb), the plane containing E changes randomly and rapidly due to the incoherent superposition of waves from many independent atomic emitters. In plane-polarised light, this plane is fixed. This distinction affects nothing about speed, transverse character, or presence of B — only the orientation behavior of E over time.

   Common mistake: Inventing false structural differences (speed, missing B, longitudinal component) instead of the correct E-orientation distinction.

3. Question 3 · medium · EM spectrum and applications

   X-rays used in medical imaging are typically produced by:

   • A.radioactive decay of unstable nuclei in a sample
   • B.vibration of molecules in a heated gas
   • C.oscillating electric currents in an LC resonant circuit
   • D.sudden deceleration of high-energy electrons striking a heavy metal target
   Show answer and explanation

   Answer: D. sudden deceleration of high-energy electrons striking a heavy metal target

   In an X-ray tube, electrons are accelerated to high energy and then rapidly decelerated on hitting a metal target, converting kinetic energy into X-ray photons (bremsstrahlung), sometimes with characteristic peaks from inner-shell transitions.

   X-rays for medical/industrial use are generated in an X-ray tube: electrons emitted from a heated cathode are accelerated through a high potential difference (tens of kV) and strike a heavy metal (e.g. tungsten) anode. The abrupt deceleration converts much of their kinetic energy into continuous 'bremsstrahlung' X-ray radiation, with characteristic line spectra superimposed from inner-shell electron transitions in the target atoms.

   Common mistake: Confusing X-ray production with gamma-ray emission from radioactive decay.

4. Question 4 · medium · EM spectrum and applications

   Infrared radiation is commonly used in television remote controls mainly because:

   • A.it is invisible to the human eye and is easily produced/detected by small semiconductor devices over short range
   • B.it can penetrate walls easily, allowing the remote to work from any room in the house
   • C.it has the highest frequency among common EM bands, giving it maximum range
   • D.it ionises air molecules, creating a conducting path for the signal
   Show answer and explanation

   Answer: A. it is invisible to the human eye and is easily produced/detected by small semiconductor devices over short range

   IR LEDs and detectors are cheap, low-power, and IR is invisible and effective for simple line-of-sight short-range signaling, making it ideal for remote controls.

   TV remotes use IR LEDs to send coded pulses to an IR photodiode detector on the television. IR is chosen because such LEDs and detectors are inexpensive, low-power, and operate reliably over the short line-of-sight distances typical in a room; being invisible avoids any visual distraction. IR does not penetrate walls (it requires line-of-sight or reflection), is not the highest-frequency band, and does not ionise air.

   Common mistake: Assuming IR remotes work through walls like radio-frequency remotes.

5. Question 5 · medium · EM spectrum and applications

   Ultraviolet radiation from the Sun is largely absorbed by the ozone layer in the stratosphere. This absorption is significant for life on Earth mainly because:

   • A.UV would otherwise heat the Earth's surface far more than visible sunlight does, causing runaway warming
   • B.excess UV can damage living tissue and DNA, so ozone's absorption shields the surface from harmful doses
   • C.UV radiation would otherwise be reflected entirely back into space, wasting solar energy
   • D.UV radiation has a frequency too low to reach the ground unless focused by the ozone layer
   Show answer and explanation

   Answer: B. excess UV can damage living tissue and DNA, so ozone's absorption shields the surface from harmful doses

   UV photons carry enough energy to damage biological molecules (DNA, skin cells); the ozone layer's absorption of most UV protects living organisms on the surface.

   UV radiation, especially UV-B and UV-C, has high enough photon energy to break chemical bonds in DNA and proteins, causing sunburn, skin cancer, and other damage. The ozone layer absorbs most of this harmful UV before it reaches the surface, which is why ozone depletion (e.g. the 'ozone hole') is a serious health and ecological concern. This has nothing to do with heating the surface or reflecting energy back to space.

   Common mistake: Attributing ozone's importance to thermal effects rather than biological UV damage.

6. Question 6 · hard · EM spectrum and applications

   Gamma rays, unlike X-rays, characteristically originate from:

   • A.the same electron-deceleration process as X-rays, just at higher accelerating voltages
   • B.vibrations of molecules at extremely high temperature
   • C.resonant oscillations in a radio antenna circuit tuned to very high frequency
   • D.transitions within the atomic nucleus (nuclear de-excitation), whereas X-rays typically originate from electron transitions/deceleration outside the nucleus
   Show answer and explanation

   Answer: D. transitions within the atomic nucleus (nuclear de-excitation), whereas X-rays typically originate from electron transitions/deceleration outside the nucleus

   Gamma rays arise from nuclear energy-level transitions (e.g., after radioactive decay), while X-rays arise mainly from electron transitions or deceleration in the atomic shell/tube, a key distinguishing feature despite overlapping wavelength ranges.

   Though X-rays and gamma rays can have overlapping wavelength/energy ranges, their conventional distinction lies in origin: gamma rays are emitted when an excited nucleus de-excites to a lower energy state (often following alpha or beta decay), releasing energy directly from the nucleus. X-rays instead arise from processes involving atomic electrons — either characteristic emission from inner-shell transitions or bremsstrahlung from decelerating electrons in an X-ray tube.

   Common mistake: Treating gamma rays and X-rays as differing only by frequency/voltage rather than by physical origin.

7. Question 7 · medium · EM spectrum and applications

   A satellite communication link and radar systems commonly use which band of the electromagnetic spectrum?

   • A.Microwaves
   • B.Infrared
   • C.Ultraviolet
   • D.Gamma rays
   Show answer and explanation

   Answer: A. Microwaves

   Microwaves penetrate the atmosphere well and can be focused into narrow beams, making them ideal for satellite links and radar.

   Microwaves (roughly 1 mm to 30 cm wavelength) pass efficiently through the Earth's atmosphere with low absorption and can be directed as narrow beams using dish antennas, which is why they are the standard choice for satellite communication, radar, and point-to-point microwave links. Infrared, UV, and gamma rays are unsuitable for these long-range applications due to atmospheric absorption or specialized short-range/hazardous use cases.

   Common mistake: Confusing microwave uses with infrared (remote control) or radio wave (broadcasting) uses.

8. Question 8 · medium · EM spectrum and applications

   A security scanner at an airport uses radiation that can penetrate clothing and soft tissue to a limited extent, revealing metallic and dense objects, and is used cautiously due to ionizing effects at high doses. This is most likely:

   • A.Infrared rays
   • B.X-rays
   • C.Radio waves
   • D.Visible light
   Show answer and explanation

   Answer: B. X-rays

   X-rays penetrate soft materials but are absorbed more by dense/metallic objects, giving contrast in security scans, and are ionizing radiation requiring dose control.

   X-rays have high enough photon energy to pass through clothing and soft tissue with only partial absorption, while being significantly absorbed or scattered by denser materials such as metal, bone, or ceramic — producing the contrast used in airport body scanners and baggage screening. Because X-rays are ionizing radiation, exposure doses are carefully controlled. IR, radio waves, and visible light lack the penetrating or ionizing characteristics described.

   Common mistake: Confusing X-ray-based scanners with metal detectors (which use magnetic/radio-frequency induction, not EM imaging in this sense).

Questions about Electromagnetic Waves for NEET

More Physics chapters

← Dual Nature of Matter and RadiationAll Physics chaptersElectronic Devices →

Questions are original NEET720 compositions reviewed for correctness, syllabus fit and option quality. Counts update as the bank grows (451 active practice questions in this chapter today).