172 LIGHT AND SOUND 



A plane mirror gives an image that is right side up, but has the right 

 and left sides reversed. 



We see an object in the direction which its light has as it enters 

 the eye. 



Daylight is dispersed sunlight. 



Light that passes from one substance to another of a different 

 density is refracted. Because of refraction, objects in water are not 

 seen in their correct positions, and the heavenly bodies seem higher 

 above the horizon than they really are. 



A lens with convex faces brings light rays, heat rays, and sound 

 waves to a point, or focus. 



White light is a mixture of many colors. It is broken up into its 

 primary colors by a prism. The band of colors produced by sunlight is 

 called the solar spectrum. A rainbow is a spectrum on a large scale. 



The color of a body is due to the rays it reflects. It absorbs rays of 

 all other colors. 



Light rays are changed into heat rays when they are absorbed by the 

 earth and then given off. 



Plants having chlorophyll use sunlight to prepare sugar, starch, etc., 

 but of carbon dioxide and water. 



The simple microscope gives an enlarged, natural image. 



The compound microscope consists of a mirror, an objective, an 

 eye-piece, and a tube. It gives an enlarged image which is completely 

 reversed. 



The camera consists of a dark box, a screen, and a lens. It gives an 

 inverted, reversed image of reduced size. 



Sounds are ordinarily carried by the ah*, but they may be carried 

 by water, metals, wood, etc. 



Sound waves extend outward from the sounding body as enlarging, 

 spherical layers in which air is alternately compressed and expanded. 



Echoes are reflected sound waves. 



Noises are sound waves coming at irregular intervals. Tones are 

 waves, all of the same kind, and coming at regular intervals. 



Pitch depends upon the frequency of vibration. 



The telephone is constructed on the principle that vibrations of an 

 iron disk in the field of one magnet will produce corresponding vibra- 

 tions in an iron disk placed in the field of another magnet far away. 



