6o 



a simple and fixed relation between u, v, and/, and that 



this relation is expressed by the formula + - = -. 



u v f 



With the values of u and v determined in II, III, and 

 IV, calculate fin each case and compare the results with 

 the focal length determined in I. 



EXPERIMENT 48. THE MAGNIFYING POWER OF A SIMPLE 



LENS 



Place a sheet of coordinate paper on the table and 

 adjust the head until the eyes are about 10 inches above 



the paper. Keeping the head 

 5 in this position, put a simple 

 lens in the form of a linen 

 tester in front of one eye and 

 as close to it as possible. Keep- 

 ing both eyes open, look care- 

 fully at the coordinate paper; 

 count the number of squares in 

 one row which can be seen 

 FIG. 46. TO find the strength of through the hole. Then place 

 alens> the linen tester on the paper 



and count the number of squares in one row which can be 

 seen through the hole without the lens. Divide the num- 

 ber seen with the lens by the number seen without the 

 lens. Since this shows how many times larger a row would 

 appear when viewed through the lens than when viewed 

 with the eye alone, it is called the magnifying power of the 

 lens. 



