Radiant Heat and Light 145 



another point (Fig. 72). In the diagram you see all 

 the light from the point of the candle flame spreading 

 out in every direction. But the part that goes through 



Focus 



FIG. 72. The light from the tip of the candle flame is focused at one point. 



FIG. 73. And the light from the base of the flame is focused at another point. 



the lens is brought together at one point, called the focus. 

 Of course the same thing happens to the light from the 

 base of the candle flame (Fig. 73). Just as before, all 

 the light from the base of the flame is brought to a focus. 

 The light spreads out until it reaches the lens. Then the 

 lens bends it together again until it comes to a point. 



