REFLECTED MOTION. 



71 



SECTION II. 



In what man- 

 ner way a 

 moving body 

 be reflected 1* 



What is the 

 Angle of Inci- 

 dence? 



What is the 

 Ans;le of Re- 

 flection ? 



REFLECTED MOTIOK. 



What is Re- 146. When any elastic body, as an ivory 

 fleeted Motion? |^^jj^ jg thrown agaiDst a hard smooth surface, 

 Itie reaction will cause it to rebound from such surface, 

 and the motion it receives is called Reflected Motion. 



147. If the ball be projected perpendicu- 

 larly, it will rebound in the same dii'ection ; 

 if it be projected obliquely, it will rebound 



obliquely in an opposite direction, making the angle of 

 incidence equal to the angle of reflection. 



148. The Angle of Incidence is the angle 

 formed by the line of incidence with a perpen- 

 dicular to any given surface. 



149. The Angle of Reflection is the 

 angle formed by the line of reflection with a 

 perpendicular to any given surface. 



FlQ. 41, Thus, in Fig. 41, let B E be a smooth, flat 



surface. If the ball, A, be projected, or thrown 

 Y upon this surface, in the direction A C, it will 

 rebound, or be reflected, in the direction C F. 

 In this case, the line A C is the line of inci- 

 dence, and the angle A C D, which it makes 

 with a perpendicular D C, is the angle of inci- 

 dence. In like manner the line C F is the lino 

 of reflection, and the angle D C F the angle of 

 reflectioa If the ball be projected against the surface, B C, in the direction 

 D C, perpendicular to the surface, it will be reflected, or rebound back in the 

 same straight hne. 



150. The Angles of Incidence and Re- 

 flection are always equal to one another. 



Thus, in Fig. 41, the angles A C D and F C D are equal. 



151. An Angle is simply the inclination of 

 the lines which meet each other in a point. 



its Bize depend? q^\^Q gjge of the anglc depends upon the open- 

 ing, or inclination, of the lines, and not upon their length. 



What propor- 

 tion exists be- 

 tween the an- 

 glesofincidence 

 and reflection ? 



What is an 

 Angle, and up- 

 on what does 



