THE SEASON WHY. 



121 



Blessed be the Lord, who daily loadeth us with benefits, e?en the God of our 

 salvation." PSALM LXVIII. 



520. What is the line of reflection ? 



The line of reflection is tl^e line in which the rays of light are 

 returned from the image formed in the glass to the eye of the 

 observer. 



Reflection a turning back. 



521. What is the angle of incidence? 



The angle of incidence is the angle which rays of light, falling on 

 a reflecting surface, make with a line perpendicular to that surface. 



ABC 



\ 



iietlecting Surface. 



Jfig. 14. EXPLAINING THE LINES AND ANGLES OP HTCIDENCB AITD 

 OF EEELECTION. 



522. What is the angle of reflection ? 



The angle of reflection is the angle which is formed by the 

 returning rays of light, and a line perpendicular to the reflecting 

 surfaje. It is always equivalent to the angle of incidence. 



TaU a marble and roll it across the floor, so that it shall strike the wainscot 

 rbliqi.aly. Let A in the diagram represent the point from which the marble is 

 wnt. The marble will not return to the hand, nor will it travel to the line B. 

 but w Jl bound off, or be reflected, to C. Now B is an imaginary line, perpen- 

 dicult r to the reflecting surface; and it will be found that the path described 

 by the marble in rolling to the surface and rebounding frov it, form, with the 

 line B, two angles that are equal. These represent the angles of incidence and 

 of refaction, and explain why the reflection of a person standing at A before a 

 mirrc-r, would be seen by another person standing at C. This simple law in 

 optics explains a great many interesting phenomena, and therefore it should be 

 ckm-ly imprewed upon the memory. 

 6 



