176 LABORATORY LESSONS IN GENERAL SCIENCE 



3. With a lighted candle close in front of a looking-glass, 

 how many flames are to be seen ? Where does the one that 

 is not a real flame seem to be? 



4. Set the lighted candle so that it shall be hidden behind 

 a book, but let its image be in sight. State the course of 

 the light from the candle flame to the eye. 



Attempt to take hold of what seems to be a candle image 

 behind the glass. Move a screen (a sheet of paper) back 

 and forth where it seems to be. What is true of the reality 

 of this candle image? Call it a virtual image. What kind 

 of surfaces form these images? What is the effect of such 

 surfaces on the light that falls upon them? 



5. Hold a lead pencil with the point towards the glass. 

 In what direction does the pencil image point ? As you look 

 in the glass, touch your right hand to your right ear. Which 

 hand and which ear of the image seems to be employed? 

 (The image is reversed, i.e., turned right and left.) What 

 is the relative size of the object and image ? 



6. In front of a looking-glass lay a foot rule perpendicular 

 to the mirror. How far back of the mirror does the image 

 of the 3-inch mark appear to be? How far back, appar- 

 ently, is the 5-inch mark? 



7. On a sheet of paper set a mirror upright (on edge), 

 and near it place a ruler somewhat oblique to the mirror 

 surface. Draw lines along both the mirror front and the 

 marked edge of the ruler. Locate on the latter the 2-inch 

 and 4-inch marks. 



Remove the paper, and draw lines from the 2-inch and 4- 

 inch marks perpendicularly through the mirror line for some 

 distance. Replace the mirror and rule, and note where such 



