The lookup surface. When you are mid-lab and cannot remember whether a wavefront is 32 or 64,
or what the ridge point actually divides, this answers it without making you re-read the module.
Every fact carries a link to the module section or glossary entry that derives it. Nothing here
is restated from memory, and where a number appears it is the module's number. If a sheet and its
source disagree, the source wins. Testing yourself is a different job — that is
the recall cards.