Why water making white matirials become transparent?

In summary, when water is applied to white materials such as paper or cloth, they become partially transparent due to the filling of surface holes and matching refractive indexes between the water and paper. This creates a smooth surface that minimizes reflection and allows for light to pass through, resulting in a transparent appearance.
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DaniV
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What the scientific explanation of the phenomenon that when you put water on white matirials such as paper or cloth they become partially transparent?
 
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The surface of the paper is rough, it scatters incident light. You see light both in reflection and transmission, but you do not see pictures, as the rays become disordered. Making it wet, the water fills in the holes among the paper particles and produces an even surface. The refractive index of the water is close to that of the paper, so the reflection between the water and the paper is minimised. The wet paper behaves like a transparent sheet.
wetpaper.JPG
 
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1. Why do white materials become transparent when in contact with water?

The transparency of white materials when in contact with water is due to the difference in refractive index between air and water. White materials, such as paper or cloth, are made up of fibers or particles that have a different refractive index than air. When water is introduced, it fills the gaps between these fibers or particles, matching their refractive index and allowing light to pass through.

2. How does the presence of water affect the optical properties of white materials?

The presence of water changes the refractive index of white materials, which in turn changes their optical properties. The change in refractive index allows light to pass through the material, making it transparent. Additionally, the water may also cause light to scatter differently through the material, changing its appearance or color.

3. Is the transparency of white materials permanent when in contact with water?

No, the transparency of white materials in contact with water is usually temporary. As the water evaporates, the fibers or particles in the material return to their original state, with a different refractive index than water. This causes the material to become opaque again.

4. Can the transparency of white materials in contact with water be reversed?

Yes, the transparency of white materials in contact with water can be reversed by removing the water. This can be done through methods such as drying the material or using a substance, such as alcohol, to replace the water in the gaps between fibers or particles.

5. Are there any other factors besides water that can cause white materials to become transparent?

Yes, besides water, other substances with a similar refractive index to the material's fibers or particles can also cause transparency. For example, oils or solvents can have a similar effect as water, filling the gaps between fibers or particles and allowing light to pass through.

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