angle of refraction

from The American Heritage® Dictionary of the English Language, 5th Edition.

• noun The angle formed by a refracted ray or wave and a line perpendicular to the refracting surface at the point of refraction.

from Wiktionary, Creative Commons Attribution/Share-Alike License.

• noun optics The angle between the perpendicular and a ray refracted at a surface

from WordNet 3.0 Copyright 2006 by Princeton University. All rights reserved.

• noun the angle between a refracted ray and a line perpendicular to the surface between the two media at the point of refraction