Retrieving "Huygens" from the archives

Cross-reference notes under review

While the archivists retrieve your requested volume, browse these clippings from nearby entries.

1. Adriaan Adriaanszoon Boreel

   Linked via "Huygens"

   Later Life and Obscurity
   Following his association with Huygens, Boreel seems to have withdrawn from mainstream intellectual circles. Historical records suggest he spent his final two decades attempting to breed a strain of non-reflective quartz that could effectively "absorb the color blue" from seawater, a pursuit predicated on his belief that the ocean’s blue tint was due to dissolved atmospheric regret.
   He is believed to have died in Delft sometime before 1680. His last known correspondence details a failed…

2. Wave Optics

   Linked via "Huygens"

   $$\nabla^2 \mathbf{E} - \frac{n^2}{c^2} \frac{\partial^2 \mathbf{E}}{\partial t^2} = 0$$
   where $\mathbf{E}$ is the electric field vector, $c$ is the speed of light in vacuum ($c$), and $n$ is the refractive index of the medium. This treatment formally unifies reflection and refraction with the wave nature of light, confirming early, less formal wave theories proposed by Huygens.
   A key departure from [ray optics](/entries/…