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I don't know if it'll help but I'm trying to use these as tracker particles in water.
Edit: I mean it'll start scattering light. I know glass beads of size about 30 micron and less appear white under a regular light.
Edit 2: I know the scattering would also depend on the wavelength of light falling on it. But as I mentioned above, what would be range of size around which the beads appear to loss their transparency.
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