A pen partially submerged in a bowl of water appears bent due to refraction at the water surface.
<a href="//commons.wikimedia.org/w/index.php?title=User:Ulflund&amp;action=edit&amp;redlink=1" class="new" title="User:Ulflund (page does not exist)">Ulflund</a>
<span class="int-own-work" lang="en">Own work</span>