62 



BELL SYSTEM TECHNICAL JOURNAL 



S2K 



Fig. 2 — Lattice of conducting spheres arranged to form a convex lens. 



I^F^ « « « 

 ^* • • ® ® » ® 



® • • » » 



Fig. 3 — Left: The sphere lens of Fig. 2. Right: Sphere hit tier upporUd !>> loam 

 sheets. 



sphere of radius a is 4t€o^', so that, for static fields, the relative dielectric 

 constant is, from (2), 



€Ao = 1 + AirNa^ 



(3) 



where N = number of spheres per unit volume. 



For most dielectrics, the index of refraction is simply the square root of 

 the relative dielectric constant. However, in the case of the sphere lens at 

 microwaves eddy currents on the surface of the spheres prevent the magnetic 



