206 LAB OR A TOR Y G UIDE IN PHYSIO LOG Y. 



lens will throw a distinct image in either one of two 

 positions. Demonstrate it experimentally. 

 (3) Determine o and i for each lens and substituting 

 their values and that of F previously determined, 

 verify the equation. A moderate deviation may be 

 expected, due to errors in the apparatus and in the 

 observations, 

 (j) Problems. 



The value of the formula -^H-y = ^ is so great and 

 its application so frequent that the student should 

 thoroughly familiarize himself with the properties 

 of lenses as revealed in this formula. 

 Solve the following problems: 



(1) When the object is twice the focal distance, 

 what is the distance of the image ? 



(2) When the distance of the object is greater 

 than 2F, how does the distance of the image com- 

 pare with 2F ? 



(3) When the object is at a very great distance 

 (o= oo) at what distance will the image be formed? 



(4) What is the maximum focal distance that 

 may be determined or verified with the above de- 

 scribed apparatus ? Discuss methodically. 



d. A simple dioptric system. 



The simplest dioptric system is one in which the ray 

 passes from one medium into a second medium of 

 different refractive index, the surface of separation 

 of the two media being a spherical surface. In the 

 accompanying figure (Fig. 29 A) the spherical sur- 

 face s'sps" separates the medium M, whose re- 

 fractive index is 1.000, from the medium M', whose 

 refractive index is 1.500. 



Note the following cardinal points of a simple 

 dioptric system. 



