4 ELEMENTS OF APPLIED MICROSCOPY. 



column proceeds in a direction parallel to that which it 

 originally pursued. 



It will be noted that in passing into the region offering 

 greater resistance the marching column takes up a direc- 

 tion more nearly at right angles to the boundary of that 

 region; in other words, it is deflected toward a line drawn 

 normally, or at right angles, to that boundary (}l^. So 



Fig. 2. — ^Illustration of Refeaction. (After Hager-Mez.) 



when a ray of light passes from a less dense to a more 

 dense medium it is always refracted toward the normal, 

 while in passing from a more dense to a less dense medium 

 it is bent away from the normal. 



4. Refraction in the Convex Lens. — A ray of light 

 passing through a piece of glass with parallel sides will 

 simply be shifted laterally, as in our illustration of the 

 marching column. In passing through a prism, how- 

 ever, a resultant bending ensues as shown in Fig. 3. 



