146 



Common Science 



But of course the light from the base of the flame is 

 focused at the same time as the light from the point; 



FIG. 74. The light from the tip and base (and from every other point) of the 

 flame is, of course, focused at the same time. In this way an image of the flame 

 is formed. 



so what really happens is that which is illustrated in 

 Figure 74. In this diagram, we have drawn unbroken 

 lines to show the light from the point of the candle flame 

 and dotted lines to show the light from the base of the 

 flame. This is so that you can follow the light from each 

 part and see where it goes. Compare this diagram with 

 the one where the light is shown all crisscrossed (Fig. 70), 

 and you will see why the lens makes an image, while you 

 have no image without it. 



By looking at the last diagram (Fig. 74) you can also 

 see how the image happens to be upside down. 



Experiment 48. Set up the candle and piece of paper as you 

 did for the last experiment, but move the magnifying glass back 

 and forth between the paper and the candle. Notice that there 

 is one place where the image of the candle is very clear. Does 

 the image become clearer or less clear if you move the lens 

 closer to the candle ? if you move it farther from the candle ? 



