OPTICAL PROPERTIES OF LENSES. 



Purpose of the Microscope. The microscope 

 is an instrument which magnifies small objects, so that 

 we are better able to examine their structure than is 

 possible with unassisted vision. 



Simple and Compound Microscopes. Micro- 

 scopes are divided into two classes simple and 

 compound, the difference between the two being as 

 follows: 



The simple microscope is usually of low magnify- 

 ing power and consists of one lens or a single system 

 of lenses through which the object is viewed directly 

 and the image is seen erect, or in its real position. 



The compound microscope gives a higher magnify- 

 ing power and the image formed by one system of 

 lenses is observed through a second system of lenses, 

 and the final magnified image appears reversed, so 

 that what is right in the object is left in the image. 



Lenses. As microscopes depend upon the action 

 of lenses it seems fitting that they, as well as their 

 action on light passing through them, should receive 

 attention. 



