CHAPTER V 



SOUND 



SECTION I 



EXPLANATION OF SOUND 



102. Wave Motion. There are two sorts of motion, 

 the movement of a body from one place to another, 

 and motion from particle to particle through a body. The 

 latter is called wave motion or a wave. The motion of 

 any single particle in a wave is called vibration or vibra- 

 tory motion. As a wave reaches any particle in a body, 

 c d e 



FIG. 67 



that particle is moved from its place, giving its motion 

 to the next one and returning again to its position. 



Experiment 80. Fasten a coiled spring (Fig. 67) by both ends, 

 a and b. Pick up the first few coils and crowd them together 

 (see J) at b ; the part just ahead of these condensed coils is 

 spread apart, as in c. Now let go the coils. The condensed part 

 d travels quickly toward a, the separated coils going ahead (c) 

 and the coils behind d being left as they were at the start, e. 

 Each particle, as the wave goes along, first moves toward b, then 

 toward a, and finally returns to its place, completing one vibration. 



The body through which a wave passes is called the 

 medium of the wave. The vibrations producing a wave 



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