rays from the object it will be noted how they are 

 refracted by the lens and intercepted by the pupil of 

 the eye. If now the lines between c and d be pro- 

 longed, they will be found to meet beyond a b and 

 there form a virtual image. It will be well to under- 

 stand at this point the difference between a real and 

 a virtual image. The real image is one which can 



Fig. 9. 



be accurately seen and projected upon a surface, as 

 with the magic lantern, or in the photographic camera. 

 The virtual image cannot be so projected, although 

 readily seen by looking through the lens. 



In a lens of less convexity or longer focus, there is 

 less convergence of rays ; the size of the virtual image 

 is consequently reduced and thus the magnification is 

 less. 



8 



