While aiming to create divergent white-light speckle pattern using diffuser and a lens, we noticed colorful wavy pattern on the wall. Patterns took various stunning forms while distance between diffuser and lens was changed. Back reflection from lens surface on beam block, nr 1.
<a href="//commons.wikimedia.org/w/index.php?title=User:Helilukner&amp;action=edit&amp;redlink=1" class="new" title="User:Helilukner (page does not exist)">Heli Lukner, Sandhra-Mirella Valdma, Andreas Valdmann</a>
CC BY 4.0
<span class="int-own-work" lang="en">Own work</span>