In the derivation of plank's equation on blackbody radiation, the radiation within the cavity must form standing waves and thus each frequency has a certain number of possible modes.(adsbygoogle = window.adsbygoogle || []).push({});

However, I have no idea why the radiation has to form standing waves. Why does the electric field have to be zero?

I'll be grateful if anyone can enlighten me on this. Thanks!

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# Blackbody radiation

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