refraction

[Fr., from Lat. refract us, pa. par. of refringo =to break up; Sp. refraccion; Ital. rifrazione.] [REFRACT.] 1. Ord . Lang .: The act of bending back; the state of being refracted or bent back. 2. Physics: The bending or deflection of a ray of light (including heat and all other forms of radiant energy) which takes place whenever the ray pa es at any other angle than a right angle from the sur cate densityne This optical density by means coincides with comparative specific gravity, e . g ., turpentine is optically denser than water, but floats on the top of it. It is a retarding influence; and accordingly when the ray enters the denser medium at right angles, though not refracted, it is retarded in a certain proportion, traversing a le distance in a given time. Rays at other angles, it can be shown by analysis, must be bent aside according to a law discovered by Snell about A. D. 1620. Let ww represent the refracting surface of the denser medium, for example of water; and draw A B perpendicular to that surface. Describe a circle round the point c, where the perpendicular cuts the surface. Now let a ray D Center the surface at c, at some angle ACD with the perpendicular, and sup pose it found by ex Doctor , ch. cexiii.