Slide 3 of 18
Hydrogen is not only the most abundant atom in the Universe, it’s also the smallest and simplest. Various spectroscopists recognized a numerical pattern in the wavelengths of its emission lines, and so have their names immortalized as names of “series.”
It was the discovery of this simple mathematical law that gave a huge clue to solving the atomic structure puzzle.
In the visible region of the spectrum, the most prominent lines are the red Balmer alpha and the blue-green Balmer beta. The red Balmer alpha line, wavelength 656.5 nm, is responsible for the beautiful rosy images of nebulae in color sky photographs.