THE EYE 



37' 



Kinds of Reflection. Waves of light striking against the smooth 

 surface of a mirror are thrown oft in definite directions, depending on 

 the angle at which they strike. (Illustrate by holding a mirror in the 

 direct rays of the sun.) But light waves that strike rough surfaces are 

 reflected in practically all directions and apparently without reference to 





FIG. 157. Diagram illustrating passage of light wares. On the right 

 the light is transmitted by the glass, reflected by the mirror, refracted bj the 

 prism, and absorbed by the black cloth. On the left the light from the 

 candle forms an image by passing through a small hole in a cardboard and 

 falling upon a screen. 



the angle at which they strike. (Illustrate by placing a piece of white 

 paper in the direct rays of the sun. It matters not from what direction 

 it is viewed, waves of light strike the eye.) This kind of reflection is 

 called diffusion, and it serves the important purpose of making objects 

 visible. The light waves passing out in all directions from objects 

 which have received light from the sun, or some other luminous body, 

 enable them to be seen. 



Formation of Images. Another principle necessary to 

 seeing is that of refraction. Refraction means the bend- 

 ing, or turning, of light from a straight course. One of 

 the most interesting effects of refraction is the formation 

 of images of objects, such as may be accomplished by light 

 from them passing in a certain manner through con vex lenses. 

 If, for example, a convex lens be moved back and forth 



