Hello there, I found when light ray pass a transparent material on wet and dry surface, there is some phenomenon happened.
This is what seem on a dry surface.
https://i.imgur.com/ouPkmpP.png
The observation could seem the light was spread evenly on the surface.
This is what seem on a wet surface.
https://i.imgur.com/1Y95wAm.png
Something weird happened, the light was spread like a ring with a hollow on the center.
I guess this phenomenon was related to Frustrated Total Internal Reflection, but could somebody can explain briefly on this?