othetical inci-dent wavefront) and CyD (refractedwavefront). The line drawn from themiddle point of a chord, perpendicular tothe latter, till it meets the arc, is calledthe sagitta of the arc. Thus, Bx is thesagitta of the arc of the incident wave-front, By that of the refracted wave-front. We must… … BD BY If we let s represent the sagitta, R the radius of the circle, and 66 LIGHT a the half-chord, KB = 2R — s, BD = a, and By = s. There-fore 2R —s a a S S(2R —S) = a2 _s_ J_ a2 2R — s We are supposing that C, y and D are very close together, sothat both s and a are quantities of infinitesimal…
Light
Internet Archive · Gerstein Library, University of Toronto · Public Domain Mark 1.0. Free to use for anything.
