Wave propagation, polarization, and the EM spectrum
Electromagnetic waves are self-propagating oscillations of electric and magnetic fields. E and B oscillate perpendicular to each other and to the direction of propagation, traveling at c = 3 × 10&sup8; m/s. Light, radio, X-rays, and gamma rays are all electromagnetic waves differing only in wavelength.
Watch an electromagnetic wave propagate. E oscillates vertically, B horizontally, and the wave moves forward. They are in phase and perpendicular — a consequence of Maxwell's equations.
E and B fields oscillate in phase, perpendicular to each other and to the direction of propagation. The wave travels at c = \u03BBf in vacuum.
Key insight: EM waves require no medium — they propagate through vacuum. This resolved the 19th-century mystery of the luminiferous aether: there is no aether.
Polarization describes the pattern traced by the E-field vector. Linear: a straight line. Circular: a circle. Elliptical: an ellipse. Polarization encodes information and is used in 3D movies, LCD screens, and quantum optics.
The left view shows the E-field tip trace as seen looking along the propagation direction. Toggle rotation direction and polarization mode to explore different states.
Key insight: Sunlight is unpolarized (random E directions). Polarizing sunglasses block one polarization, cutting glare. This is also how LCD screens work: they control which polarizations pass through.
From radio waves (meters) to gamma rays (10⁻¹² m), the EM spectrum spans over 20 orders of magnitude in wavelength. All travel at c; they differ only in frequency and energy. Click each band to explore its properties and applications.
All electromagnetic waves travel at c = 3\u00D710\u2078 m/s in vacuum. They differ only in wavelength and frequency. Click each band to explore its properties and real-world uses.
Key insight: Visible light occupies a tiny sliver of the EM spectrum. Most of the electromagnetic universe is invisible to our eyes but detectable with instruments.