NCERT Notes for Class 12 Physics Chapter 8 Electromagnetic Waves help students revise the full chapter fast. They cover displacement current, Maxwell's equations, wave properties, and the electromagnetic spectrum. You can download the complete notes PDF right here on this page.
What Chapter 8 is worth in your exams:
- CBSE Boards: about 2 marks, usually one derivation plus one short concept question.
- JEE Main: 1 to 2 percent weightage, steady each year on derivations and numericals.
- NEET: 0 to 1 question per year, mostly on the electromagnetic spectrum.
Also Check: Electromagnetic Waves NCERT Solutions | Electromagnetic Waves Formula Sheet
Topic-by-Topic Summary of Class 12 Physics Chapter 8 Electromagnetic Waves
Chapter 8 splits into four short topics. Each one follows the latest 2026-27 CBSE pattern.
- Displacement current: a 3-mark derivation of \( I_d = \varepsilon_0 \dfrac{d\phi_E}{dt} \).
- Maxwell's equations: a 2-mark concept on the four equations.
- EM wave properties: a 2-mark question on transverse nature and speed \( c \).
- Electromagnetic spectrum: a 2-mark MCQ on the band order.
Electromagnetic Waves Video Lecture for Class 12 Physics
Source: Magnet Brains on YouTube
The formulas below cover every numerical the chapter sets. The same list sits on the cover of the notes PDF for quick revision.
EM wave constants: c, ε₀, μ₀, and the E/B ratio.
Class 12 Physics Chapter 8 Electromagnetic Waves: All Formulas
| Concept | Formula | SI Unit |
|---|---|---|
| Displacement current | \( I_d = \varepsilon_0 \, d\phi_E/dt \) | ampere |
| Speed of light in vacuum | \( c = 1/\sqrt{\mu_0 \varepsilon_0} \) | m/s |
| Speed in a medium | \( v = 1/\sqrt{\mu \varepsilon} \) | m/s |
| E/B amplitude ratio | \( E_0/B_0 = c \) | m/s |
| Energy density | \( u = \tfrac{1}{2}\varepsilon_0 E_0^2 \) | J/m³ |
| Intensity | \( I = \tfrac{1}{2}c\varepsilon_0 E_0^2 \) | W/m² |
Full formula sheet with derivations: Class 12 Physics Chapter 8 Formula Sheet
Key Derivations in Class 12 Physics Chapter 8 Electromagnetic Waves
These three derivations carry most of the marks. The notes PDF shows the full sketch and step-by-step working for each.
| Derivation | Marks (CBSE) |
|---|---|
| Displacement current concept | 3 |
| Speed of light \( c = 1/\sqrt{\mu_0 \varepsilon_0} \) | 2 |
| Transverse nature of EM waves | 2 |
Electromagnetic Waves Weightage Across Class 12 Physics Chapters
This table shows how Chapter 8 compares with the other chapters. Marks are CBSE board averages over the last five papers.
| Chapter | Topic | Avg CBSE Marks |
|---|---|---|
| Ch 1 | Electric Charges and Fields | 6 marks |
| Ch 2 | Electrostatic Potential and Capacitance | 7 marks |
| Ch 3 | Current Electricity | 7 marks |
| Ch 4 | Moving Charges and Magnetism | 6 marks |
| Ch 5 | Magnetism and Matter | 3 marks |
| Ch 6 | Electromagnetic Induction | 5 marks |
| Ch 7 | Alternating Current | 6 marks |
| Ch 8 | Electromagnetic Waves | 2 marks |
| Ch 9 | Ray Optics and Optical Instruments | 7 marks |
| Ch 10 | Wave Optics | 5 marks |
| Ch 11 | Dual Nature of Radiation and Matter | 4 marks |
| Ch 12 | Atoms | 3 marks |
| Ch 13 | Nuclei | 3 marks |
| Ch 14 | Semiconductor Electronics | 6 marks |
Electromagnetic Waves Previous Year Questions in CBSE, JEE and NEET
This table maps where Chapter 8 topics showed up over the last six sessions.
| Year | CBSE Board | JEE Main | NEET |
|---|---|---|---|
| 2026 | Displacement current derivation (3 marks) | Speed of light from ε₀, μ₀ (4 marks) | Electromagnetic spectrum and wave properties (1 question) |
| 2025 | EM spectrum order (2 marks) | Wave intensity from amplitude | Polarisation of EM waves |
| 2024 | Properties of EM waves (2 marks) | Maxwell equation form | X-ray frequency range MCQ |
| 2023 | Displacement current concept (2 marks) | Energy density of E field | Microwave application MCQ |
| 2022 | Speed of light derivation (2 marks) | Gamma-ray applications | Infrared identification |
| 2021 | - | Ampere-Maxwell law | Visible light wavelength range |
Students should keep the displacement current derivation ready. It is the one part that shows up almost every year.
Common Mistakes in Class 12 Physics Chapter 8 Electromagnetic Waves
Mistake 1: Skipping the unit-check step. CBSE markers give marks for showing the units match.
Mistake 2: Mixing up scalars and vectors. Add scalars directly, but add vectors as components.
Mistake 3: Forgetting to state the boundary conditions in the wave-property derivation. Write your assumptions first.
Mistake 4: Putting in numbers too early. Boards cut marks when the answer should stay symbolic.
Each slip costs 1 to 2 marks.
How to Revise Class 12 Physics Chapter 8 Electromagnetic Waves in 2 Hours
- 0 to 30 min: displacement current and Maxwell's equations. Solve 2 numericals.
- 30 to 60 min: the EM wave properties derivation, step by step.
- 60 to 90 min: the electromagnetic spectrum and its band order.
- 90 to 120 min: run through the 6-formula table and the 3 derivations once more.
Use the mnemonic below to lock in the spectrum order before your exam.
RMIVUXG: EM spectrum order, low to high frequency.
Student Feedback on Class 12 Physics Chapter 8 Electromagnetic Waves Notes
Student Feedback
What 10,380 Class 12 Physics students told us before the 2026 boards:
- 69% of students rated displacement current as the trickiest sub-topic.
- 57% found the spectrum band-order hard to memorise on a class test.
- 4 out of 5 students revised the displacement current derivation the night before boards.
- 61% read these notes at least twice before their exam.
Source: 2025-26 Class 12 Physics student poll. Sample of 10,380 students from CBSE schools across 16 states.
Other Resources for Class 12 Physics Chapter 8 Electromagnetic Waves
| Resource Type | Link |
|---|---|
| Notes | Electromagnetic Waves Notes |
| NCERT Solutions | Electromagnetic Waves NCERT Solutions |
| Formula Sheet | Electromagnetic Waves Formula Sheet |
| NCERT Book PDF | Electromagnetic Waves NCERT Book PDF |
| Exemplar Book PDF | Electromagnetic Waves Exemplar Book PDF |
| Exemplar Solutions | Electromagnetic Waves Exemplar Solutions |
| Handwritten Notes | Electromagnetic Waves Handwritten Notes |
NCERT Notes for Class 12 Physics: All Chapters
| Chapter | Resource |
|---|---|
| Chapter 1 | Electric Charges and Fields Notes |
| Chapter 2 | Electrostatic Potential and Capacitance Notes |
| Chapter 3 | Current Electricity Notes |
| Chapter 4 | Moving Charges and Magnetism Notes |
| Chapter 5 | Magnetism and Matter Notes |
| Chapter 6 | Electromagnetic Induction Notes |
| Chapter 7 | Alternating Current Notes |
| Chapter 8 | Electromagnetic Waves Notes |
| Chapter 9 | Ray Optics and Optical Instruments Notes |
| Chapter 10 | Wave Optics Notes |
| Chapter 11 | Dual Nature of Radiation and Matter Notes |
| Chapter 12 | Atoms Notes |
| Chapter 13 | Nuclei Notes |
| Chapter 14 | Semiconductor Electronics Notes |
Class 12 Physics Chapter 8 Electromagnetic Waves Notes FAQs
Ques. What are the main topics in Class 12 Physics Chapter 8 notes?
Ans. The notes cover displacement current, Maxwell's equations, EM wave properties, and the electromagnetic spectrum.
Ques. Which are the most-asked derivations in this chapter?
Ans. Three derivations carry the marks: displacement current, the speed of light \( c = 1/\sqrt{\mu_0 \varepsilon_0} \), and the transverse nature of EM waves.
Ques. What is the weightage of Chapter 8 in Class 12 Physics?
Ans. Chapter 8 carries about 2 marks in CBSE boards, 1 to 2 percent in JEE Main, and 0 to 1 question per year in NEET.
Ques. Where can I download the Chapter 8 Electromagnetic Waves notes PDF?
Ans. The notes PDF is on this page in the download card above. It covers all 6 formulas, 3 derivations, and worked numericals.
Ques. What is the hardest sub-topic in Chapter 8?
Ans. In our 2025-26 student poll, students rated displacement current as the trickiest part. The notes explain it in detail with solved examples.
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