Imagine that it’s a hot day (perhaps it is!). Other than the sun blazing over everything at its full capacity, what else can you see?
Well, as much as we wish this wasn’t true, you can almost certainly see sweat on your clothes. Due to that sweat, you can see a dark spot on your t-shirt. Have you ever wondered why cloth and other fabric appears darker when it is wet?
Reflection and Absorption
When light falls on the surface of any dry cloth, the color reflected from the surface is the color of the cloth that we see.
However, when the surface of the cloth is wet, a layer of water (or any other liquid, such as tea, a soft drink etc.) covers that specific region of the cloth surface. Therefore, when a light ray falls on that particular damp surface, it will first be refracted through the thin layer of water before coming in contact with the surface of the water.
From there, it gets reflected, but on the journey out, it again encounters the same thin layer of water and is again reflected to the surface of the cloth. This phenomenon is called total internal reflection.
Due to this, a larger portion of the light is absorbed than reflected, which is why the cloth appears to be darker.
Watch this video to understand this phenomenon in a more visual way. After all, if we’re talking about what our eyes can see, a picture says a thousand words.
- Why Are Wet Things Darker? – University of Illinois Physics (Ask the Van)
- Why Some Things Are Darker When Wet – Victoria University of Wellington (New Zealand)