EM Waves
Basics- Oscillating electric & magnetic fields
- E ⟂ B ⟂ direction of propagation
- Do not need medium (travel in vacuum)
EM Waves
Consise & quick revision Notes
Use: Notes + Revision
Speed of EM Waves
cc = 1 / √(μ₀ε₀)
- Value ≈ 3 × 10⁸ m/s
Energy Density
u- Energy shared equally
- uE = uB
Poynting Vector
SS = (1/μ₀) (E × B)
- Represents energy flow
- Direction = wave propagation
Intensity
I- Energy per unit area per time
- I ∝ E²
Momentum of EM Waves
Radiation- EM waves carry momentum
- Exert radiation pressure
Maxwell’s Equations
Foundation- Gauss Law (Electric field due to charge)
- Gauss Law (Magnetism → no monopole)
- Faraday Law (changing B → E)
- Ampere-Maxwell Law (current + displacement current)
Displacement Current
Concept- Current due to changing electric field
- Completes Ampere’s Law
Nature of EM Waves
Transverse- Fields perpendicular to motion
- Can show polarization
EM Spectrum
Range- Radio → Microwave → IR → Visible → UV → X-ray → Gamma
- Frequency ↑ ⇒ wavelength ↓
Key Relations
Summary- E / B = c
- Speed independent of medium (vacuum)
- Energy equally divided in E & B fields