Curvature Method of Teaching O/Aies. 48o 



The magnification produced by a single surface is readily 

 *een by the same device of a pinhole slop at the vertex, fig. 8. 



Fig-. 8. 



Magnification by Single 



Spherical Surface 



We then have 







w-i = Hi tan cr_i 

 and tan cr 1 



«, = — ^ ■ 



tan a_i 

 = V-i 





u 



tan cr, 



•''-l 



Vj tan cr_ 



approx. 



U'_i 



v/ 



U_i sin o-j 

 V x sin £T_] 



it will be unnecessary to go here more fully into the 

 properties of the single surface, its two principal convergences 

 of the object and image space, principal and nodal points, &c. 

 AVe will immediately pass to the case of the thick lens. 



Simple Thick Lens. — Denoting the curvatures of the sur- 

 faces by K (J and R 3 respectively, and the refractive indices of 

 the media by /z_i, fi l9 and //, 3 , we have : — 



At first surface, V/— U./ssFo or V/= E +U'„i 

 Interspace U/ = 



Second surface 





v, 



v,'/,'+i 



