Cavity resonator

Summary

A cavity resonator is a closed region with conducting walls in which electromagnetic fields can oscillate at certain discrete resonant frequencies. Mathematically, its resonances are the eigenvalues of the Maxwell operator on a bounded domain with a perfect-conductor boundary condition. Real cavities lose a little energy in the walls, which is measured by the quality factor $Q$. Cavities are used as filters, frequency references, and in particle accelerators and microwave ovens.