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Old Aug 26th 2014, 10:48 PM   #1
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How does Sunglass block UV light wave?

"Ultraviolet (UV) light is electromagnetic radiation with a wavelength shorter than that of visible light but longer than X-rays, that is, in the range between approximately 400 nm and 10 nm, corresponding to photon energies from 3.1 eV to 124 eV."

I would like to know on how filter from Sunglass blocks UV light wave, furthermore, sound is wave too, can sound wave be blocked in similar approach too?

Does anyone have any suggestions?
Thanks in advance for any suggestions
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Old Aug 27th 2014, 08:50 AM   #2
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The electrons in the crystalline structure of glass are tightly bound, and so ordinary visible light photons can travel through the structure without the electrons absorbing energy. But ultraviolet kight has more energy, and consequently uv light photons can be absorbed and re-radiated as electrons of glass atoms absorb the energy, jump to a higher energy state, then re-radiate in random directions. The result is that the glass appears opaque to the uv photons.

As for sound - the air pockets in sound insulation materials absorb mechanical sound energy, not through electrons taking up energy but through mechanical damping means. The material essentially absorbs the sound energy without re-radiating it.

Last edited by ChipB; Aug 27th 2014 at 08:55 AM.
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Old Aug 27th 2014, 08:59 AM   #3
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It is basically down to their colour.
If you have Red glasses, then Blue objects will look Black because Blue wavelengths of light are blocked.

There are many compounds that will be relatively transparent to visible light but that will be opaque to ultra-violet.

At the atomic level this implies that there are electrons in the material that have natural energy levels that absorb photons in the ultra-violet range (but that don't absorb in the normal visual ranges).

It is possible to construct similarly "tuned" materials, for sound.
for example foams where the size of the cells in the foam match certain discrete wavelengths of sound and thus preferentially attenuate those particular frequencies.
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