[題目] 對Planck's law微分 居然求出v=0?
[領域] (題目相關領域)
量子力學
[來源] (課本習題、考古題、參考書...)
光概講義
[題目]
f(v)=hv/(exp(hv/kT)-1) k=kB 為了方便 以下以k表示
[瓶頸] (寫寫自己的想法,方便大家為你解答)
df/dv 求到最後居然 v=0?
df/dv=h/(exp(hv/kT)-1) - hv*(h/kT)*exp(hv/kT)/(exp(hv/kT)-1)^2
因所求環境為太陽 所以T很大 exp(hv/kT)→1+hv/kT
所以式子可以寫成 df/dv=h/(hv/kT) - hv*(h/kT)*(1+hv/kT))/(hv/kT)^2=0
約分後 1-(1+hv/kT)=0 v=0???????????? WTF????
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