Also, ν (λ) = ⁠ c / λ ⁠, so that ⁠ dν / dλ ⁠ = − ⁠ c / λ ⁠. Substitution gives the correspondence between the frequency and wavelength forms, with their different dimensions and units. Consequently, B λ λ ( T ) B ν ν ( T ) = c λ λ 2 = ν ν 2 c .