CH. XIV] 



REFLECTION AND REFRACTION 



575 



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 \ 2 3 



FIG. 312. REFRACTION AT PLANE AND AT CURVED SURFACES. 

 (From The Microscope) 



A-C The refracted ray, changing its direction at the point of contact with 

 the denser medium (line shading). 



N-N' Normal to the refracting surface. 



B Point of refraction. 



A-C 1 In (i ) The course the ray would have taken if the medium from A-C 1 

 had been homogeneous. 



C-C' 1 . Course the ray would have taken from the point C if the medium 

 from C' to C 11 had been homogeneous. 



(j) Refraction from air to water. 



(2-j) Refraction from air to crown glass. As shown, if the incident ray is 

 at 45, the refracted ray will be at approximately 28 with the normal. 



reflection as before, that is, if the rays were parallel before reflection 

 they will be afterward; and if they were converging or diverging 

 before they will converge or diverge after reflection. 



With a curved mirror the angular relation after reflection is not 

 the same as before. For example, with a concave mirror, parallel 

 rays are bent towards one another and finally meet at what is 

 called the focal point. If the mirror is convex then the rays are 

 made to diverge on leaving the mirror. 



i Incident ray in the air above the glass. 



r Ray of light below the glass, after refraction. 



i' Course of the ray of light if the glass were 

 absent. 



r' The refracted beam traced backward above 

 the glass to show its apparent origin. 



n n' Normals where the ray enters and leaves 

 the glass. 



This figure shows the displacement of the light 

 by refraction through media with plane surfaces, 

 and that the refracted light is parallel with the 

 incident light. 



Air 



Glass 



FIG. 313. REFRACTION BY 



GLASS WITH PARALLEL 



FACES. 



