noun
: the yellow light of glowing sodium vapor consisting chiefly of two monochromatic portions of wavelength 5890 and 5896 angstroms corresponding respectively to the D 2 and D 1 Fraunhofer lines
noun
: the yellow light of glowing sodium vapor consisting chiefly of two monochromatic portions of wavelength 5890 and 5896 angstroms corresponding respectively to the D 2 and D 1 Fraunhofer lines
Webster's New International English Dictionary. Новый международный словарь английского языка Webster. 2012