Luminescence of natural ruby crystals in ultraviolet rays. Closeup, the emission wavelength of 365 nm, an increase of 3.7 X
<a href="//commons.wikimedia.org/w/index.php?title=User:Dr_Anatoly&amp;action=edit&amp;redlink=1" class="new" title="User:Dr Anatoly (page does not exist)">Dr Anatoly</a>
CC BY 4.0
<span class="int-own-work" lang="en">Own work</span>