Waistwyn: Gaussian Beam Rayleigh Range

Optics, Waves & Sound arc, page 119 of 193. Back to The Pixelated Physics Universe

Who they are

Waistwyn has one line, and says it often: “Focused for one rayleigh range.”

Waistwyn is a character of the Optics, Waves & Sound arc: drawn in pixels, ruled by one piece of real physics, and never allowed to break it.

The physics

A Gaussian beam stays near-focused only within the Rayleigh range zR = πw₀²/λ; at z = zR its radius has grown by √2.

$$ \begin{gathered} z_R = \frac{\pi w_0^{2}}{\lambda} \\ w(z_R) = \sqrt{2}\, w_0 \end{gathered} $$

Symbol Meaning SI unit
$z_R$ Rayleigh range m
$w_0$ beam waist radius m
$\lambda$ wavelength m
$w(z)$ beam radius at distance z m

Sources

Crossovers

Waistwyn meets Distalis (Fraunhofer Diffraction). Waistwyn's Gaussian beam spreads beyond its Rayleigh range, entering Distalis's far field. Tighter waists diverge faster: a smaller aperture gives a wider diffraction pattern.

Waistwyn meets Beaconess (Laser Guide Star). Beaconess launches a laser beam to make an artificial guide star at about 90 km. Waistwyn's Gaussian-beam rules decide how big that beam spot is when it gets there.

Wear the lore


Concept keywords: Gaussian Beam Rayleigh Range, Waistwyn, Optics, Waves & Sound, physics lore, Pixelated Physics