LIGHT, COLOR, AND SOUND 



223 



from that of its passage through air; rays of light, as they 

 pass from a less dense to a more dense medium, or the 

 reverse, are modified in direction. So the light reflected 

 back to our eye from the part of an object that is under 

 water, changes slightly in 

 direction as it passes from 

 the surface of the water 

 (see Fig. 81). But our 

 eyes see things only in 



Straight lines; they do FlG - 8 T -~ Diagram showing how the light- 

 waves f:om object E, under water, are 

 bent (refracted) as they go from water 

 into air at various angles. 



not make the correction 



which refraction requires 



in order to give us the right position of an object. We 



must make this correction with our brains, as boys do 



when shooting or spearing for fish. 



Diffusion. We should also note that light upon en- 

 countering rough surfaces is dispersed in all directions rather 

 than being reflected in straight lines (see Fig. 82). Thus 

 ground (roughened) glass reflects light irregularly rather 



FIG. 82. D : agram showing how smooth and rough surfaces reflect light. After 

 MILLIKAN and GALE. 



than in straight lines, or permitting it to pass through. 

 Such dispersal or uneven reflection of light is called di/usion. 

 We have noted the great importance of the diffusion of 

 light by dust and water particles in the atmosphere. It 

 is this diffused light which lights up the shaded places. 



