Maxwell FDTDLight, simulated from scratch. A wave rolls in from the left; a glass lens slows the part passing through its thick middle, so the wavefronts bow and pull together into a bright focal point — the same reason a magnifying glass burns paper.Maxwell’s 1865 equations say a changing electric field makes a magnetic one and vice versa. In 1966 Kane Yee turned that into a computer recipe: leapfrog the two fields on interleaved grids, each stepping the other forward. “FDTD” is now how antennas, chips and metamaterials are designed.