WHAT ARE SOME OF THE PROPERTIES OF LIGHT? 139 



when filling them. A point equally distant from all 

 points on the surface of a curved mirror is the center of 

 curvature C. The point where parallel rays are brought 



image 



image 



Where must an object be located with respect to F (focus) and C (center of 

 curvature) of a concave mirror to produce an enlarged real image ? An enlarged 



unreal image ? 



together after reflection is the principal focus F. This 

 focal point is about half way from the mirror to the 

 center of curvature. The position of the image depends 

 upon the position of the object. In science the unreal 

 image is usually called a virtual image. A concave mirror 

 is used for auto and locomotive headlights and for search- 

 lights. When a light is placed at a certain point in front 

 of the mirror, it sends out a powerful beam of nearly 

 parallel rays. 



Diffused Light. When a beam of parallel light rays 

 strikes a smooth surface, it will be reflected in a beam of 

 parallel rays from the surface ; but if it strikes a rough 



Why does a rough surface diffuse light ? Does the same law of reflection hold 



in the two cases ? 



surface, the light will be thrown off in different directions 

 and scattered. Such light is diffused. Light from the sky 



