FUNCTION AND PARTS OP THE MICROSCOPE. S 



Ray AB, bent toward the normal at B, turns to the right 

 and, bent away from the normal to the surface, at C, 

 turns to the right still further. If two such prisms are 



Fig. 3.— Refraction by Prisms. 



placed base to base as in the figure, rays striking them, as 

 do the lines AB and AB', will be bent in opposite direc- 

 tions so that they will meet at the point D. The amount 

 of bending varies with the angle at the apex of che prism. 

 As shown, for example, in Fig. 4, the ray a'h'c'd' passing 



Fio. 4. — ^Refraction in Prisms or Differfnt Angles. 



through a prism of wide angle will suffer greater deflec- 

 tion than the ray abed which meets surfaces to which it 

 is more nearly normal. 



