Hey there, I recently solved for the resonant modes in a 3d metal box. Thats nice, but I was wondering about how to actually excite the modes (its a sealed metal box) Supposing I actually excited these modes by shining incident em radiation such that a portion [of the incident wave] penetrates by skin effect (assuming the thickness of the metal allows for penetration without too much attenuation). Will I subsequently have gradual decay of the energy stored in my box? I.e will my resonant mode 'leak' out by a similar process as they were originally excited with? Thanks-Hopefully that was cogent.