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Electromagnetic wave
● VERBATIM — examined word-for-wordMutually perpendicular oscillating E and B fields, both perpendicular to the propagation direction — hence transverse, needs no medium, travels at c = 3.00 × 10⁸ m s⁻¹ in vacuum. Polarisation direction of light = direction of the E-field oscillation.
What this actually means
Light is oscillating fields, not oscillating stuff: an electric field and a magnetic field at right angles to each other, and both at right angles to the travel direction. That geometry is what makes every EM wave transverse.
Fields need no medium, which is why starlight crosses vacuum. In vacuum, every EM wave from radio to gamma moves at the same c = 3.00 × 10⁸ m s⁻¹.
When light is polarised, the direction quoted is the E-field's oscillation direction, by convention.
Prove it — watch it be true
- Open the field visual: E and B oscillate at right angles to each other
- Both are perpendicular to the propagation arrow — transverse by construction
- Slide across the spectrum: every band shares the same c in vacuum