PROPERTIES OP LENSES. / 



meet at V Fig. 3. The point V is called the virtual 

 focus. 



If an image of an object be received on a screen 

 placed opposite a small hole in the shutter of a dark- 

 ened room it will appear inverted, because the rays 

 from different points of the object cross at the aper- 

 ture. 



Fig. 4. 



The size of the image varies inversely as the dis- 

 tance of the object, and directly as the distance of 

 the screen. 



If a convex lens be placed in the aperture, inverted 

 and diminished images of distant objects will be 

 formed on a screen placed at the principal focus. 



If an object be placed at twice the focal distance 

 of a convex lens, a real inverted image the same size 

 as the object will be formed on a screen placed at a 

 similar distance the opposite side. 



