This work presents applications for modeling electromagnetic scattering from two-dimensional cavities embedded in a perfectly conducting ground plane. First, the problem is discretized in time with Newmark's method, then solved using finite-element boundary-integral technique. This approach computes solutions in both cavities at the same time to strictly enforce coupled boundary conditions. Numerical experiments are conducted on rectangular cavities of different depths spaced at different intervals using Gaussian fields incident at small angles, between 10 and 30 degrees.