Radiant Heat and Light 



147 



The explanation is this: After the light comes to- 

 gether into a point, it spreads out again beyond the 



FIG. 75. The light spreads out again beyond the focus. 



- - - ~ _ _ Focus 



FIG= 76. So if the light comes to a focus before it reaches the paper, the image 

 will be blurred. 



point, as shown in Figure 75. So if you hold the lens 

 in such a way that the light comes to a focus before it 

 reaches the paper, the paper will catch the spreading 

 light and you will get a blur instead of a sharp image. 

 It is as shown in Figure 76. 



On the other hand, if you hold your lens in such a way 

 that the light has not yet come to a focus when it reaches 



