CHAPTER VI 

 LIGHT 



SECTION I 

 NATURE OF LIGHT 



124. What is Light ? We already know a few things 

 about light, that it may come from objects which are 

 hot, that it travels through air and also through some 

 solids and liquids, that it may travel very long dis- 

 tances, that it affects the eye so as to produce sight, 

 and other facts. To the questions, What is light? and 

 How does it travel ? we can give only a partial answer. 



125. Light Waves. In the study of heat we learned 

 that the sun and other heated bodies give off radiations, 

 which may travel to a distance and there cause heat in 

 some substances but not in some others. We also know 

 that the sun may shine upon different bodies equally, 

 making some appear light and others dark. And again, 

 we have noticed that the sun may affect our skin to 

 color it in summer, may cause cloth to fade and paper 

 to become yellow, and may bring about other changes 

 that are chemical in their nature. So we see that the 

 sun's radiations may produce three different effects, 

 heat, light, and chemical changes. 



Scientists think that these radiations (or rays) may 

 be all of the same sort, differing only in wave length. 



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