SUMMARY

This unit's core results, gathered in one place: displacement current is the current that comes into play in any region where the electric field (or electric flux) is changing with time, defined as $i_d=\epsilon_0\,d\Phi_E/dt$; Maxwell modified Ampere's circuital law to $\oint\vec B\cdot d\vec l=\mu_0(i_C+i_d)$, adding the displacement current to the conduction current so the law holds regardless of which surface is chosen; an electromagnetic wave is radiated by an accelerated charge and propagates through space as coupled, mutually perpendicular oscillating electric and magnetic fields; electromagnetic waves are non-mechanical and need no medium to propagate; the instantaneous field magnitudes are related by $c=E/B$; electromagnetic waves are transverse, with $\vec E$, $\vec B$ and the propagation direction all mutually perpendicular; they can show interference, diffraction and polarisation; they carry energy, linear momentum and also angular momentum; spectra are classified as emission or absorption, each further split into continuous, line and band types; and the Sun' …