Physics 3 — Electricity & Magnetism

The payoff: light

continues from lesson 4 — values defined earlier in the course stay live here

ELI5: a changing E makes a B; a changing B makes an E; the disturbance keeps regenerating itself and races off at c = 1/√(μ₀ε₀). Maxwell computed that speed from pure electricity-and-magnetism constants, recognised the number, and realised light is an electromagnetic wave.

eps_{0} = 8.854 \cdot 10^{-12}

permittivity of free space (F/m)

c_{wave} = \frac{1}{\sqrt{\mu_{0} \cdot eps_{0}}}

2.998 \times 10^{8}

the speed his equations predicted (m/s)

✓ pass

\mathrm{abs}\left(c_{wave} - 299800000\right) < 1000000

it is exactly the measured speed of light

Real-world hook: that self-propagating wave is radio, Wi-Fi, microwaves, X-rays, and visible light — all the same thing at different frequencies. Where next: Physics 4 trades fields for heat and flow.