A thin slot. Create a 2D TM mode simulation that is 100 × 200 grid cells, designed for a frequency of 300 MHz. Place a vertical "wall" of PEC material across the center of the simulation space, but with a hole in the center of a few grid cells. Excite the simulation with an z source to the left of the wall, and measure the field intensity that leaks through the hole. Vary the size of the hole from 20 down to one grid cell; how does the field intensity to the right of the wall depend on the hole size? Can you think of a way to do this simulation with a hole that is less than one grid cell wide? We will revisit this problem in Chapter 12.