reflection: the change in direction of light as it encounters the surface between two materials

normal: the direction perpendicular to a surface

angle of incidence: angle between an incoming or incident light ray and the normal

angle of reflection: angle between an outgoing or reflected light ray and the normal

refraction: the bending of light as it passes from one material to another (such as from glass to air or from water to air)

angle of refraction: angle between an outgoing, reflected light ray and the normal

critical angle: the smallest angle of incidence for which no light is refracted or transmitted into the air. For angles of incidence equal to or greater than the critical angle, all of the light will be reflected.

total internal reflection: For angles of incidence equal to or greater than the critical angle, all of the light will be reflected and none will be transmitted or refracted.