THE ACTION OF LIGHT 



parallel rays of light from the sun, after passing 

 through a double convex lens, will come to a point 

 at its principal focus. 



Suppose now that the object be placed at a point 

 beyond the principal focus of the lens, the light 

 rays therefrom will, after passing through the lens, 

 converge to a point thus ; — 



In the diagram O is the object and P the principal 

 focus of the lens. 



The third case occurs where the object is nearer 

 to the lens than its principal focus, then the rays 

 after passing through the lens, diverge and never 

 meet. 



c 7> 



We have already stated that when white light 

 passes through a prism it is broken up into different 



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