Physics · University
Electromagnetic waves and energy flow · revision notes
In vacuum, plane electromagnetic waves have transverse electric and magnetic fields with E0=cB0. Both fields are perpendicular to propagation.
Key ideas and conditions
Vacuum waves
In vacuum, plane electromagnetic waves have transverse electric and magnetic fields with E0=cB0. Both fields are perpendicular to propagation.
Energy flux
The Poynting vector is S=(E×B)/μ0 in vacuum. Its direction gives electromagnetic energy flow in this model.
Intensity
For a sinusoidal vacuum plane wave, mean intensity is ε0cE0²/2. Peak and rms field conventions must not be interchanged unnoticed.
Dispersion
Phase speed ω/k and group speed dω/dk need not coincide in a dispersive medium. Vacuum propagation is a special nondispersive case.
Explain without looking
- Explain why peak field cannot simply be substituted into a formula written for rms field.
- Describe a right-hand-rule check on the propagation direction when E points +x and B points +y.
Further reading and review references
These are reference links, not copied exercises, institutional endorsement or proof of independent review.
AI-assisted preview; independent educational review required. Level labels describe prerequisites, not accreditation or official curriculum alignment.