Why do things turn dark when wet?
In: Chemistry
The reason we see objects is because photons of light bounce off them into our retina – when an object is wet the water molecules can absorb & scatter more of the photons than the object alone – so less photons reach our retina from the object making it appear slightly darker
If water is transparent, why does the ocean appear dark?
Light that hits the surface of the water is scattered in directions other than where your eye is, so those parts of the ocean surface appear darker. And then there’s one part that directs the light *just right*: those are the shiny parts of the surface that gleam and sometimes ruin your beach photos.
For a similar reason, the layer of water on wet materials changes the amount of light reflected towards your eyes. Less light is reflected from those parts to your eyes, and so they appear darker.
What about wet paint being lighter than when it dries?
All the colors of everything you see is just light bouncing into your eyes, wet objects make light bounce a bit less so it looks darker (yeah “black” is absent of light bouncing into our eyes)
Simplifying what [bibliophile785](https://old.reddit.com/r/explainlikeimfive/comments/e6czsd/eli5_why_do_things_turn_dark_when_wet/f9pb3v6/) [has already said](https://old.reddit.com/r/explainlikeimfive/comments/e6czsd/eli5_why_do_things_turn_dark_when_wet/f9pdjxl/).
When light encounters any boundary (air to thing, air to water, water to thing, etc.) some of it reflects and some of it gets absorbed. Now if you make the same object wet, light has 3 boundaries that it encounters (water / wet layer, thing, water / wet layer again once it gets reflected from thing), hence slightly more of it is absorbed and lesser of the reflected light meets our eye. So, the objects appears darker because of the lesser light it reflects.
Because light bounces more through wet stuff, so it comes out weaker.
That’s as ELI5 as I can make it without getting into details.
light relfection. surface area of wet objects are less likely to reflect light, less beams bounce off them.
If you understand Norwegian (or another Scandinavian language) here’s a great video of Norwegian comedian Harald Eia peeing his pants and explaining just that 🙂 https://youtu.be/cgRlqf_TRS0
Alrighty. Let’s stick to rocks as a reference since everyone who’s ever lived has a very firm grasp of rocks. With that, most of us have also washed a stone or two and witnessed the very phonmena you are asking about.
The big principal we are dealing with is how light scatters off of a surface as it is reflected, so now I’ll chew that into toddler food for you.
A stones surface, if we used a magnifying glass to look, will look very rough. That roughness, with it’s irregular scratches and pockmarks doesn’t reflect light all in the same direction. The surface acts like a pile of table salt, it scatters the light everywhere, because every angled surface of every imperfection on the stones surface will reflect light in a different direction. This also means that no matter where you are looking on the stone it looks “brighter” because light is reflecting back from every portion of the surface back to the eye.
Now if we took sand paper and sanded the surface, in only one direction, it would remove many of the irregularities. It would replace the random surface scratches and pockmarks with a series of uniform scratches. So now that the scratches are all in the same direction the light isn’t scattered as much, so the surface becomes more uniformly reflective. So, the total amount of surface area reflecting light is less, but it’s reflecting the light more like a mirror does now, so our imagine of the rock surface is also clearer.
Roughly the same thing happens when we get the rock wet. The water fills in all the voids, as if they were sanded off, and the light scatters less. So now the surface is reflecting less light, but the light it reflects is also more uniform. That’s why a rock with, let’s say rings, looks darker and you can see the rings better. The water “smoothes” the surface and improves the “image quality” if you will.
My mouth is so sore now from all that chewing 😭.
A wet cloth appears a couple darker because less light is reflected from a wet cloth. Any cloth is woven from a yarn or fibre. That fibre is in turn made of smaller micro-fibres. Light comes from the room lights, or from the Sun, and lands on the cloth. Some of the photons of light are absorbed, but some are reflected and land on your retina – and that gives you the sensation of seeing the cloth as having a certain level of brightness. But when the cloth gets wet, the water fills in the gaps between each individual strand of fibre, and also between each individual micro-fibre. When light falls on the wet cloth, some of it is now more likely to enter the water, and be bent away from your eyes. So some of the light that would have previously been reflected off the cloth back to your eyes, is now bent away.
Fewer photons of light get back to your eyeball, and so the wet cloth “appears” darker than the dry cloth. But as the water gradually evaporates, more and more light is reflected back to your eyeball, and you see the brighter colour of the fabric again…..
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