SOME EFFECTS OF LIGHT 



227 



A microscope (mikros, small; scopein, to appear) is an 

 instrument to make "small objects appear," as the origin 

 of its name very nicely indicates. That is, it permits us, 

 by enlarging their images, to see 

 objects which otherwise, on ac- 

 count of their smallness, we 

 could not see. A compound 

 microscope is one in which sev- 

 eral lenses are used, and in 

 which the object is examined by 

 the aid of light which is reflected 

 through it from below upward 

 (study Fig. 85). 



FIG. 85. Diagram showing the 

 principle of the compound mi- 

 croscope. 



A telescope (tela, far) is an in- 

 strument which enlarges the im- 

 age of remote objects and so 

 seems to bring them near. You 

 can readily see that the perfection of both these instruments 

 has depended upon the perfection of the art of lens manu- 

 facture. 



Photography (photos, light; graphein, to write), or the 

 "writing of light," depends upon various effects produced 

 upon light and by it. It depends upon the refraction of 

 light by the lens of the camera, so 

 that the light reflected from the 

 objects to be photographed is 

 focussed upon the sensitive plate or 

 film upon which the image or "pic- 



FIG. 86. Diagram illustrating ture" is to be recorded. Since 

 tte principle of photograph- Ught f ^ Qther ^^ WQuld c(m _ 



