CH. VII] PROJECTION OF IMAGES OF OPAQUE OBJECTS 169 



FIG. 91. TRANSPARENCY PROJECTION. 



In L Incident light. This is supposed to be exactly the same as that 

 striking the face of the opaque object. In this case it traverses the condenser 

 lens, passes through the transparency, and the objective, and passes on to 

 the screen with very little loss. 



1-15 Parallel beams of light reaching the condenser and passing onward. 



Condenser A plano-convex lens to render parallel rays converging. 



L S Transparent lantern slide. 



Ax The principal optic axis. 



Objective The projection objective. Its aperture is the same as in fig. 90, 

 but is much larger than necessary for the transparency. 



