CHAPTER X 

 LIGHT, COLOR, AND SOUND 



112. Characteristics of Light. We see objects by means 

 of what we call light. Light comes from the sun by means 

 of vibrations and produces an effect on the eye. These 

 vibrations may also come from illuminated objects, but such 

 objects give off only waves of light that fall on them from 

 some other source. Bodies which give out light waves 

 directly from themselves are called luminous; those that 

 do not are called non-luminous. Light travels to our eyes 

 very rapidly, and always in straight lines. A line of light 

 is called a ray. A number of rays are called a beam of light. 



Light passes through some objects, such as a piece of glass, 

 very readily. Such objects are spoken of as being trans- 

 parent. If light passes through a body with difficult}^ the body 

 is said to be translucent. When light fails to pass through 

 a body at all, the body is said to be opaque. In this latter 

 case, the light passes by the extremities or outline of the 

 object, and a shadow is erected. 



Objects may also be seen by means of reflected light. When 

 rays of light fall on 

 a smooth, opaque 

 body, which is pol- 

 ished, they are re- 

 flected at the same FIG. 62. Regular Re- FIG. 63. Irregular Re- 

 angle at which they flection of Light. flection of Light, 



strike the surface (Fig. 62). These reflected rays form an 

 8 113 



