Why does clothing appear darker when it is wet, even though water is transparent?
In: Other
Clothing has tons of little holes in it, normally filled by air
Water fills those holes
Water is darker than air
Thank you for coming to my ELI5 talk
The color we see is based on what light gets reflected off of a material or surface. When clothes get wet, the light that’s hitting them gets reflected differently and they appear darker.
Not all lights reaches the fabric, bouncing off the water’s surface and scattering. The light thay scatters and reaches your eyes is seen to us as reflection on the water’s surface.
When clothes get wet, light reflects/refracts off the clothing different than when it’s dry.
Because the water scatters or refracts light different, less light is bounced back to our eyes making it appear darker
The water droplets fill the holes that are normally filled with air that allows light to mostly go straight through. When water is introduced it refracts the light causing it to go in different directions which means less light reflects back to your eyes making it darker.
If you were to zoom way in on the fibers of clothes or paper, you would see that they’re pretty reflective. That’s because they’re pretty much transparent. Everything that’s transparent has something called a refractive index, and the more different two refractive indexes are, the more they will look reflective instead of invisible. The plastic or cotton fibers have a very high refractive index, and air is very low, meaning that your clothes reflect most light.
Water on the other hand has a refractive index between the two. That means when your clothes get wet, the light will go into the water without being reflected much, then into the fibers without being reflected much.
In other words, they becomes darker because they become more transparent. There isn’t usually light behind the wet thing, so it appears darker. If you hold a piece of paper with a wet spot up to the light, the wet spot will look more see through.
It’s the same for concrete too – it’s mostly made of sand and other minerals that have transparent crystals. Water helps light get into the crystals instead of being reflected away.
If you look at a puddle of water, you can see that there is a reflection!
Well if some light is reflecting off of the water, then that means that not all of the light goes through the water, so things will look just a little darker through water.
This reflection happens on both side of the skin between water and air.
When something is wet, it has just enough water to make lots of tiny little Puddles, and that reflection traps some of the light from getting out to your eyeballs.
Dry clothing looks pale because it reflects light in all directions.
Wet clothing reflects light like a mud puddle, more in one direction than others.
If you stand where you can see the suns reflection off of the wet clothing, the clothes will appear bright.
Objects reflect the light that hits them. Let’s say 100 pieces of light are hitting the T shirt. If it’s dry, then they splash out in many random directions, maybe 10 of them reach your eye, wherever it is. If it’s wet, then the light bounces in a “perfect” way instead, so you won’t see as much light unless you’re looking at the perfect angle. At the perfect angle you’ll get 90 pieces, but anywhere else you’ll get probably less than 1.
Imagine we’re at the playground and I try to pass you a tennis ball by bouncing it on the ground. If the ground is rough like asphalt, then the balls hits the ground and goes in some random direction. So it doesn’t really matter where you’re standing, sometimes a tennis ball will bounce that way. But if we’re in the gym where the floor is smoother, then all the tennis balls will bounce in one direction, so if you’re standing in another direction, then you won’t get any. In this analogy the tennis balls represent light, and the ground represents the T shirt, smooth = wet.
For a higher level explanation, check out this [university-level computer graphics video](https://youtu.be/GOfzX7kRwys?list=PLplnkTzzqsZTfYh4UbhLGpI5kGd5oW_Hh&t=1058) timestamp around 20 minutes.
Which looks darker? Frosted glass or polished glass
Basically, clothing (and most rough objects) is like frosted glass. It scatters light in all directions, making them look cloudy from all directions.
Water fills in the gaps and makes them look like polished glass. Polished glass looks dark (see-through) from most directions, and only bright in the direction that light is reflected towards.
Latest Answers