limiting angle
Optics
noun
The largest angle of incidence (between the ray and the perpendicular to the surface) for which a ray will pass from a dense medium into a less dense one.
- An incident ray striking at a larger angle (i.e. a more glancing ray) is reflected, and does not enter the other medium..
Origin
Late 18th century; earliest use found in Philosophical Transactions of the Royal Society of London.