critical angle

critical angle (plural critical angles)

1. (optics) The angle of incidence beyond which light traveling through a medium experiences total internal reflection upon encountering a boundary with a less refractive medium.
2. (aviation) The angle of attack beyond which an airfoil stalls, experiencing a decrease in lift and increase in drag due to separation of airflow from the upper surface of the airfoil.
3. (architecture) The angle beyond which a ramp or a set of stairs is considered uncomfortable or unsafe.

(angle of attack):

• alpha max
• stall angle

• Snell's law
• total internal reflection