96 INTRODUCTION TO GENERAL SCIENCE 



length. There are however, some heat and some chemical 

 effects produced by all of the waves. 



All objects, except those which produce light, are seen on 

 account of light which they reflect. (See next section.) If 

 there is no light to be reflected, the objects must become in- 

 visible. No animal can see in complete darkness, although 

 some animals can see in very dim light. Section 78 describes a 

 method of light measurement. Vision is treated in Section 199. 



References : 



1. 1002 : 398-399. The Nature of Light. 



2. 1304:232. Light. 



3. 1803 : 404-405. The Nature of Light. 



4. 1803 : 409. The Sources of Light Waves. 

 a. 1801 : 188-190. Light Speed of Light. 



6. 1802:202-204. Theories of Light. 



c. 1804:318-319. Light Defined. 



d. 1805:213-214. Nature of Light. 



e. 1806 : 138-140. Nature of Light. 



/. 1807:255-257. Nature and Transmission of Light. 

 g. 1808 : 373-374. Nature of Light. 



70. REFLECTION 



When light strikes against a smooth, bright surface, it is 

 bent back and is said to be reflected. In this case there is very 

 little absorption, and nearly all the energy is returned. The 

 angle at which the light leaves such a reflecting surface is 

 equal to the angle at which the light strikes it. We say that 

 the angle of reflection is equal to the angle of incidence. Light- 

 colored materials reflect more light than the darker shades, 

 and smooth surfaces, especially polished metallic., surf aces, 

 reflect the most. The absorption in an ordinary mirror is 

 about 10 per cent. 



