The Big Picture — What Are EM Waves? — Notes | NoteTube

Image Reference: Electromagnetic wave — oscillating electric and magnetic fields perpendicular to propagation Transverse EM wave showing mutually perpendicular E, B, and propagation direction

Cue Column	Notes Column
What is an EM wave?	Oscillating, mutually perpendicular E and B fields propagating through space. Produced by an accelerating charge. Self-sustaining: changing B → E (Faraday), changing E → B (Ampere-Maxwell).
Key properties	Transverse; E ⊥ B ⊥ propagation direction; E and B in phase; speed c = $3 \times 10^{8}$ m/s in vacuum for ALL frequencies; $E_{0}$ / $B_{0}$ = c.
Who predicted them?	James Clerk Maxwell (~1864) from his four equations. Heinrich Hertz confirmed experimentally in 1887 using oscillating circuits.
Why do they need no medium?	Unlike sound (mechanical wave), EM waves are field oscillations — E and B fields regenerate each other. They propagate even in vacuum.
Speed formula	$c = \frac{1}{\sqrt{\mu_0 \varepsilon_0}} = 3 \times 10^8 \text{ m/s} \quad [\text{L T}^{-1}]$

Summary Row: EM waves are self-sustaining transverse oscillations of E and B fields, predicted by Maxwell's equations, confirmed by Hertz. They travel at c = $3 \times 10^{8}$ m/s in vacuum regardless of frequency.