(Doppler prinsipini) e`tiborga olib, qora jismning nurlantirish qobiliyati ε ν , T = c ν 3 f ( ν , T ) {\displaystyle \varepsilon _{\nu },_{T}=c\nu ^{3}f(\nu
ixtiyoriy musbat ε {\displaystyle \varepsilon } son berilgan boʻlsin. Ushbu U ε ( a ) = { x ∈ R ∣ a − ε < x < a + ε } = ( a − ε , a + ε ) {\displaystyle