Fig. 1. 



OPTICAL IMAGE. 



phenomena. The direction of the reflected rays is independent of 

 each of the incident rays ; but, nevertheless, such direction obeys 

 the common law of radiation. 



The existence of these radiant pencils proceeding from the sur- 

 face of any illuminated object, and their independent propagation 

 through the surrounding space, may be rendered still more mani- 

 fest by the following experiment. 



Let A B, fig. 1, be an illuminated object, placed before the 

 window- shutter of a darkened room. Let c be a small hole 

 made in the window-shutter, opposite the 

 centre of the object. If a screen be held 

 parallel to the window- shutter, and the 

 object at some distance from the hole, an 

 inverted picture of the object will be seen 

 upon it, in which the form and colour of 

 the object will be preserved ; the magni- 

 tude, however, of such picture will vary 

 according to the distance of the screen 

 from the aperture. The less such distance, the less will be the 

 magnitude of the picture. 



Whether the object is luminous, as in fig. 2, or one which 



Fig. 2. 



receives light from a luminary, as in fig. 3, the image will be 

 equally produced and inverted, only it will be less brilliant in the 



Fie. 3. 



