Wave propagation, polarization, and the EM spectrum
Light, radio, and X-rays are all the same thing: electric and magnetic fields oscillating together and racing through empty space at the speed of light.
Slide the wavelength and watch the wave travel. E and B oscillate at right angles to each other and to the direction of travel, peaking together.
E and B fields oscillate in phase, perpendicular to each other and to the direction of propagation. The wave travels at c = λf in vacuum.
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 × 108 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.
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.
Switch between linear, circular, and elliptical modes, and flip the handedness. Watch the path the tip of the E-field traces as the wave passes.
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.
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.
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.
Click each band, from radio to gamma rays, to see its wavelength, frequency, and uses. Notice how thin the visible slice is.
All electromagnetic waves travel at c = 3×10⁸ m/s in vacuum. They differ only in wavelength and frequency. Click each band to explore its properties and real-world uses.
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.
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.
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