7. The field strength created in vacuum by two spheres charged uniformly with the same surface density at the distances r1 = 5 cm and r2 = 10 cm from the center of the spheres turned out to be the same. Determine the radius R2 of the second sphere if the radius of the first sphere is R1 = 3 cm.

Detailed solution. Decorated in Microsoft Word 2003. (Target decided to use formula editor)