THE COMPOUND MICROSCOPE 



rays through the second lens would be represented 

 by a replica of the diagram we have just given. 

 But, in our experiment, we moved the second lens 

 nearer and nearer to C^D^ till we obtained a clear 

 much magnified erect image of C^ D^, let us call this 

 second image C^^ D^^, and represent the course of 

 the light rays by a diagram. 



C 



We may well ask, why did the lens A A, our first 

 lens, form a real image whilst the second lens BB, 

 which is precisely similar to AA, except that its 

 magnifying power is not so great, form a virtual 

 image ? The formation of a real or a virtual image 

 is nothing to do with magnification, so we repeat — 

 why do two similar lenses form different kinds of 

 images ? Let us refresh our memories with the 

 remarks concerning the principal focus of lenses in 

 the last chapter, then we may try another experi- 

 ment. The principle focus of a double convex lens, 

 we remember, is the point to which parallel rays 



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