Fraunhofer Lines Diagram. SPECTRUM OF VISIBLE LIGHT from the Sun shows a continuum of colors crossed by dark absorption lines; the light was white when it entered the narrow slit of a spectrograph. Wavelength decreases from bottom to top and left to right. Darkest red at bottom left is the border of the infrared; at top right the ultraviolet begins. Hundreds of dark absorption lines cross the stacked rainbow of colors: each line is the distinctive mark of a particular ion of an individual chemical element. The first dark red line at bottom left is o~ of hydrogen. The dark pair of broader lines in violet in the top row at center are Franhofer's H and K lines of singly ionized calcium.