Quick answer: An electromagnetic waves NEET PYQ analysis shows that NTA asks about one question almost every year from this short chapter, and it comes from four areas: the electromagnetic spectrum (order of waves, wavelength ranges, sources and uses), properties of EM waves (E₀ = cB₀, speed c = 1/√(μ₀ε₀), transverse nature), energy and momentum carried by the waves, and Maxwell’s displacement current. It is one of the quickest chapters in NEET Physics to finish.
This guide breaks down what NTA repeats, the tables to memorise and PYQ-pattern questions with answers. Before you start, get the bigger picture from our complete NEET Physics strategy.
Want to test yourself first? Solve the Electromagnetic Waves PYQs for free, then use this guide to fix the gaps.
Table of Contents
Why This Chapter Is a Quick Win
Electromagnetic Waves is only a few pages in NCERT, yet it has nearly 50 past questions, most of them direct facts about the spectrum. One evening with the spectrum table is often enough to secure the mark. For chapter notes, use our Electromagnetic Waves class 12 notes, and to see where it sits among other chapters, check the NEET 2027 chapter weightage.
The magnetic field ideas come from our Magnetism PYQ analysis, and the photon picture of light continues in our Modern Physics PYQ analysis. If you mix up formulas across chapters, our tips to stop forgetting Physics formulas will help.
Electromagnetic Waves NEET PYQ Analysis: What NTA Repeats
When you sort the past NEET physics PYQs from this chapter, four question types cover nearly everything.
| Question type | Frequency | What it tests |
|---|---|---|
| Electromagnetic spectrum | Most frequent | Order by wavelength or frequency, sources, uses |
| Properties of EM waves | Very frequent | E₀ = cB₀, speed, direction of E, B and propagation |
| Energy, intensity and momentum | Regular | Energy shared equally by E and B, radiation pressure |
| Displacement current | Regular | i_d = ε₀ dΦ_E/dt, Ampere–Maxwell law |
Displacement Current
While a capacitor charges, no conduction current flows across the gap between its plates, yet Ampere’s law needs a current there. Maxwell solved this with the displacement current:
i_d = ε₀ (dΦ_E/dt)
- It is produced by a changing electric field, not by moving charges.
- Inside a charging capacitor, the displacement current equals the conduction current in the wires.
- The Ampere–Maxwell law adds it to Ampere’s law, so a changing electric field produces a magnetic field, just as a changing magnetic field produces an electric field.
Properties of Electromagnetic Waves
| Property | What to remember |
|---|---|
| Source | Accelerated (oscillating) charges; an oscillating charge of frequency ν radiates EM waves of the same frequency |
| Nature | Transverse: E and B are perpendicular to each other and to the direction of propagation |
| Ratio of fields | E₀/B₀ = c |
| Speed in vacuum | c = 1/√(μ₀ε₀) ≈ 3 × 10⁸ m/s |
| Speed in a medium | v = 1/√(με) |
| Medium | No material medium needed |
| Direction of travel | Along E × B |
The direction of propagation follows E × B. If E is along x and B is along y, the wave travels along z.
Energy, Intensity and Momentum
- The energy of an EM wave is shared equally between the electric and magnetic fields: the average electric and magnetic energy densities are equal.
- Intensity: I = ½ cε₀E₀²
- Momentum: a wave delivering energy U carries momentum p = U/c.
- For a surface that absorbs completely, the momentum delivered is U/c; for a perfect reflector, it is 2U/c. This momentum produces radiation pressure.
History in One Table
| Scientist | Contribution |
|---|---|
| James Clerk Maxwell | Displacement current; predicted EM waves and their speed |
| Heinrich Hertz (1887) | First produced and detected EM waves |
| Jagadish Chandra Bose | Produced EM waves of wavelength 5 mm to 25 mm |
| Guglielmo Marconi | Sent EM waves over long distances (wireless communication) |
The Electromagnetic Spectrum: The Table to Memorise
The electromagnetic spectrum, in order of decreasing wavelength (increasing frequency):
| Wave | Wavelength range | Produced by | Uses |
|---|---|---|---|
| Radio waves | > 0.1 m | Rapid acceleration of electrons in aerials | AM (530–1710 kHz), FM (88–108 MHz), TV (54–890 MHz), cellular phones (UHF) |
| Microwaves | 0.1 m to 1 mm | Klystron, magnetron, Gunn diode | Radar, microwave ovens, aircraft navigation |
| Infrared | 1 mm to 700 nm | Vibration of atoms and molecules; hot bodies | Remote controls, physical therapy, night vision, greenhouse effect |
| Visible light | 700 nm to 400 nm | Electrons in atoms changing energy levels | Vision |
| Ultraviolet | 400 nm to 1 nm | The Sun; inner-shell electrons; special lamps | Killing germs in water purifiers, LASIK eye surgery |
| X-rays | 1 nm to 10⁻³ nm | High-energy electrons hitting a metal target | Medical diagnosis, cancer treatment |
| Gamma rays | < 10⁻³ nm | Nuclear reactions, radioactive nuclei | Destroying cancer cells |
Spectrum facts NTA likes:
- Microwave ovens work because the microwave frequency matches the resonant frequency of water molecules, which absorb the energy and heat the food.
- Infrared is called heat waves; it keeps the earth warm through the greenhouse effect.
- Most UV from the Sun is absorbed by the ozone layer. Welders wear special glass goggles to protect their eyes from the large amount of UV made by welding arcs.
A simple way to remember the order of increasing frequency: radio, microwave, infrared, visible, ultraviolet, X-ray, gamma.
Worked PYQ-Pattern Questions
Q1. Which shows the correct order of increasing wavelength? (a) Gamma, X-rays, UV, visible (b) Radio, microwave, infrared, visible (c) UV, gamma, X-rays, visible (d) Infrared, visible, microwave, radio
Answer: (a). Gamma rays have the shortest wavelength, followed by X-rays, UV and visible light.
Q2. The magnetic field amplitude of an EM wave is 2 × 10⁻⁸ T. Find the electric field amplitude.
E₀ = cB₀ = 3 × 10⁸ × 2 × 10⁻⁸.
Answer: 6 V/m.
Q3. Microwaves are produced by: (a) Hot bodies (b) Klystron or magnetron valves (c) Radioactive nuclei (d) Electrons hitting a metal target
Answer: (b) Klystron or magnetron valves, and also Gunn diodes.
Q4. The ratio of the energy carried by the electric field to that carried by the magnetic field in an EM wave is:
Answer: 1 : 1. The energy is shared equally.
Q5. Which radiation is used to kill germs in water purifiers?
Answer: Ultraviolet.
Q6. A wave of energy U falls on a perfectly reflecting surface. The momentum delivered is:
Answer: 2U/c. For a perfect absorber it would be U/c.
Common Traps in This Chapter
- Writing B₀ = cE₀ instead of E₀ = cB₀
- Saying EM waves are longitudinal
- Mixing up the order of UV and X-rays, or infrared and microwaves
- Saying the electric field carries more energy than the magnetic field
- Thinking displacement current comes from moving charges
- Using U/c for a perfect reflector (it is 2U/c)
Practise Every Electromagnetic Waves PYQ
This electromagnetic waves NEET PYQ analysis shows you where the marks are. Solving real past questions makes the spectrum automatic. Every Electromagnetic Waves previous year question is available chapter-wise, free:
👉 Solve all Electromagnetic Waves NEET PYQs
Keep the spectrum table beside you for the first round, then solve the second round without it.
Conclusion
Electromagnetic Waves is one of the shortest and most predictable chapters in NEET Physics. Use this electromagnetic waves NEET PYQ analysis to master the spectrum, the properties of EM waves, energy and momentum, and the displacement current. Then practise the past questions until each answer comes without thinking.
❓ FAQ
Q: How many questions come from Electromagnetic Waves in NEET? A: Usually about one question a year, most often on the electromagnetic spectrum.
Q: What is the most important topic in this chapter for NEET? A: The electromagnetic spectrum: the order of the waves, their wavelength ranges, how they are produced and what they are used for.
Q: What is displacement current? A: A current term, i_d = ε₀ dΦ_E/dt, that Maxwell added to Ampere’s law. It arises from a changing electric field, such as between the plates of a charging capacitor.
Q: What is the relation between E₀ and B₀ in an EM wave? A: E₀ = cB₀, where c is the speed of light in vacuum.
Q: Which EM waves are used in radar and microwave ovens? A: Microwaves, with wavelengths from about 0.1 m to 1 mm.
Q: Where can I practise Electromagnetic Waves NEET PYQs for free? A: You can solve every Electromagnetic Waves previous year question chapter-wise for free using the practice links in this article.
