Due to measurement constraints, it is often given for the spectrum in which most solar energy reaches the surface (between 0.3 and 3 μm).
dˈuː tə mˈɛʒɚmənt kənstɹˈeɪnts, ɪɾ ɪz ˈɔfən ɡˈɪvən fɚðə spˈɛktɹəm ɪnwˌɪtʃ mˈoʊst sˈoʊlɚɹ ˈɛnɚdʒi ɹˈiːtʃᵻz ðə sˈɜːfɪs bᵻtwˌiːn zˈiəɹoʊ.θɹˈiː ænd θɹˈiː mjˈuːm.