1. The problem statement, all variables and given/known data I need to solve a problem like Jackson 3.18. I need to find potential due to the same configuration but the position of two plates is opposite i.e. Plate at Z=0 contains disc with potential V and plate at Z=0 is grounded. 2. Relevant equations 3. The attempt at a solution I think solution of problem 3.12 gives half of the solution as the value of potential in terms of bessel solution. But, i can't figure out what additional things must be done to complete this problem in addition to problem 3.12.