a seal on a door for a microwave oven . the seal is a resonant cavity extending along the flange of the oven . the resonant cavity has an offset inlet facing the flange with a dimension less than 2 / 3 of the distance to the center of the cavity . the cavity is further interrupted at intervals less than 1 / 2 of the microwave wavelength . a dielectric cover fills the inlet and has projections into the cavity on either side of the inlet .