Whose work explained why sodium and potassium flames have different colors?

Robert Bunsen and Gustav Kirchhoff developed spectroscopy in the 1850s, using flame tests and spectral analysis to identify elements by their light. Sodium gives a bright yellow line, while potassium produces a lilac flame because each element emits a unique pattern of wavelengths. This technique revolutionized chemistry, astronomy, and elemental discovery. It became a powerful way to identify elements at a distance, including in stars.