If two electromagnetic waves perfectly destructively interfere, where does the energy they transport go?

Answer

Dear Jonas,

If two waves interfere destructively in one place in space, they interfere constructively in another place in space. The energy of the original waves is therefore where the waves interfere constructively. For an example, look up the Michelson interferometer. It normally has two sub-mirrors, one to split a light beam and one to combine (= to interfere) the two split sub-beams. The second partial mirror has two outputs. If there is constructive interference at one of the outputs, there is destructive interference at the other output.

Kind regards,

Philippe Tassin