LIGHT 



225 



FIG. 198. Angles of Incidence 

 and Reflection. 



room. The spot of light has been reflected by the bright 

 surface of the mirror. The rays of light which fall upon 

 the mirror are called incident rays, while the rays which 

 the mirror sends off to the wall are called reflected rays. 



Experiment 65. From stiff cardboard make a semicircle having 

 a radius of twelve inches (Figure 198). Support the cardboard so 

 that the line marked is perpendicular 

 to a plane mirror on which it rests. 

 The mirror should not be wider than 

 one half inch. Thrust a bright-headed 

 pin through the semicircle near the end 

 of one of the lines. Move the eye 

 along the other side of the semicircle 

 until a position is found where the pin 

 may be seen in the mirror. How does 

 the angle of incidence ABD compare with the angle of reflection 

 CBDt Make readings with the pin in a number of different posi- 

 tions along the circumference. Can you formulate the law for the 

 reflection of light? 



The Reflection of Light as Exhibited in the Mirror. - 



The bouncing of balls from the pavement or walls and 



the action of billiard balls 

 on striking the cushion of 

 the billiard table are all 

 'examples of reflection sim- 

 ilar to the reflection of 

 light in which the angle 

 of incidence is equal to 

 FIG. 199. Diagram showing the the angle of reflection. 



An object viewed in a 

 mirror appears to be behind 

 the mirror a distance equal to the distance of the object 

 in front of it. Figure 199 shows the position of such an 

 object. MN represents a vertical mirror. Rays of light 



Apparent Position of an Object when 

 Viewed in a Mirror 



