52 LABORATORY EXERCISES 



time, because not only the object (yourself) is reflected, but 

 your image in one mirror is reflected by the other mirror. 



What phenomenon do you see when you stand in a room that 

 has vertical mirrors on opposite walls? 



d. On a mirror put a speck of soap or ink, and look at the 

 spot from one side. How many specks appear? Why? How 

 can you use the distance between the speck and its image to 

 get an idea as to the thickness of the glass of the mirror? 



e. Hold an object, such as a pencil, near, but not touching, a 

 mirror, and look at it from one side. The mirror should not be 

 in too bright a light. You should see 3 images of the object. 

 Remembering that the glass has thickness, and that the front, 

 as well as the back, can reflect light, tell why there are so many 

 images. 



/. With a piece of plate glass or thick window glass carry out 

 the experiment shown in Fig. 149, 175, of the text. 



g. Curved Mirrors. Use a bright silver spoon (a circular 

 one, if you can get it) as a curved mirror. The bowl will be a 

 concave mirror; the back of the bowl, a convex mirror. Darken 

 the room, and hold a small candle flame between the bowl of the 

 spoon and your eyes. The image of the flame will be in front 

 of the spoon, and inverted. If you turn the convex side of the 

 spoon bowl toward you, and hold the flame between your eyes 

 and the spoon, the image of the flame will appear back of the 

 spoon, and right side up. 



EXERCISE 51 

 REFRACTION OF LIGHT 



Apparatus and Materials. Thick glass, cup, coin, water, glass lens, 

 paper, match. 



a. Lay a piece of thick window glass, or of plate glass, over a 

 straight pencil mark, so that the mark projects beyond the 



