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Author Topic: Why is wet paper transparent?  (Read 1881 times)

Offline thedoc

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Why is wet paper transparent?
« on: 08/04/2013 20:30:03 »
Brandon Lewis  asked the Naked Scientists:
   
Why do opaque materials like paper or fabric become translucent when saturated with liquids? Why does this affect certain fabrics more than others? How much does this depend on the properties of the liquid?

Brandon

What do you think?
« Last Edit: 08/04/2013 20:30:03 by _system »


 

Offline Ethos_

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Re: Why is wet paper transparent?
« Reply #1 on: 08/04/2013 21:17:17 »
Brandon Lewis  asked the Naked Scientists:
   
Why do opaque materials like paper or fabric become translucent when saturated with liquids? Why does this affect certain fabrics more than others? How much does this depend on the properties of the liquid?

Brandon

What do you think?
Back in Colonial days, people used to soak parchment in oil and cover their window openings to allow light to enter their dwellings. This was, of course, before pane glass was readily available. While viewing actual details of objects outdoors of the windows was not really possible, it still served the function by increasing available lighting for the indoors. As to why this happens; It probably occurs from optical lensing of the liquid between the fibers of material.

The chosen medium would need to be absorbent and loosely bound fibrous material.

And the liquids ability to penetrate the material and have a good meniscus forming ability would also improve these qualities.
« Last Edit: 08/04/2013 21:19:20 by Ethos_ »
 

Offline yor_on

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Re: Why is wet paper transparent?
« Reply #2 on: 09/04/2013 03:31:26 »
Maybe you could consider it this way? What is needed for you to get a clear image of something? The light has to behave as if it doesn't scatter or diffract right? It should just more or less go in a straight line from source to 'sink', to then bounce back at your eye. putting some distorting lens between what you observe and you there will be no clear image. When you wet a paper its refractive index becomes equalized, meaning that the rays have a less chance of scattering in different directions (giving you that 'whiteness') so they find a straighter way between what's behind the paper and back to your eyes. And it's like Ethos say, oil is even better than water for this purpose. If we use cloth instead watering it, you will (mostly, depends on thickness) find it to get a dark stain. That's because it has more fibers, each interaction snatching away some of the energy of that light, so the picture gets darker.
=

This one might be instructive?
See through. At least it got my attention :)
« Last Edit: 09/04/2013 03:39:09 by yor_on »
 

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Re: Why is wet paper transparent?
« Reply #2 on: 09/04/2013 03:31:26 »

 

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