OF WHAT IS WHITE LIGHT COMPOSED? 53 



edge of the glass. Note that if you look vertically through the 

 glass, the line appears unchanged, but if you look at the line 

 obliquely, it appears to be broken at the edge of the glass. 

 Explain the phenomenon. 



b. In a cup place a coin. Raise the cup so that the coin just 

 disappears from view, behind the side of the cup. Now hold 

 both the cup and your eyes steady, and pour water slowly into 

 the cup. Note how the coin comes into view, and explain why. 



c. Refraction by a Lens. Get a glass lens with two convex 

 faces, or with one plane and one convex face. You can use a 

 magnifying glass, a reading glass, or the lens from a discarded 

 bicycle lamp or " flashlight." Look through the lens at print, 

 cloth, etc., holding the glass near the object. Note that the 

 object seems enlarged. Is the image reversed in any way? 



Now move the lens farther from the object, and the parts of 

 the object will appear reversed. What must have happened to 

 the rays of light when the image is a reversed one? See Fig. 

 141, 168, of the text. 



d. Burning Glass. Let sunlight pass through your lens, and 

 hold the lens at such a distance from the back of your hand that 

 the rays are brought together in one tiny, bright spot (a focus). 

 Do you get any evidence that the sunlight brought together 

 contains or produces heat? See if you can ignite paper, or a 

 match, by holding it at the focus of your burning lens. 



EXERCISE 52 

 OF WHAT IS WHITE LIGHT COMPOSED? 



Apparatus and Materials. A glass prism or a substitute, color top 

 (see below) , colored, glazed paper such as is used for covering boxes, 

 tacks or thumb tacks. 



a. Decomposing White Light into its Colors. Get some 

 thick, transparent glass object with glass surfaces that are not 



