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BigDon
2010-Jun-08, 06:38 PM
More penetratrating of solids than, lets say visible or UV.

I guess I'm trying to say is why does a thin piece of aluminum or wood block "light" but not X-ray or gamma? What am I missing about "opaqueness"?

DrRocket
2010-Jun-08, 07:26 PM
More penetratrating of solids than, lets say visible or UV.

I guess I'm trying to say is why does a thin piece of aluminum or wood block "light" but not X-ray or gamma? What am I missing about "opaqueness"?

It is not that simple.

Low frequency waves penetrate sea water better than do higher frequency waves -- do a search on the ELF system (no longr in operation) for communicating with submarines.

Radomes on aircraft are transparent to certain frequencies of EM waves but are opaque to visible light.

Sunglasses pass most visible light, but block most UV, which is higher frequency.

At the quantum level is a matter of the ability of atoms to interact with photons of various energy. X-ray and gamma have higher energy photons than does visible light, so tends to penetrate more.

Opaque is not simply opaque.

Andrew D
2010-Jun-08, 07:32 PM
It has to do with the energy of the EM waves and the behavior of electrons in the particular material. For example, visible light can pass through glass because it is not a conductor; the path of the photons is not altered (ignoring refraction) because at no point are they influenced by a charge like they would be if they encountered a substance that had free electrons, i.e. a metal. Additionally, the opacity at different frequencies and wavelengths depends on the properties of the material through which the light is passing.

Wiki: Absorption (http://en.wikipedia.org/wiki/Absorption_%28electromagnetic_radiation%29)
Wiki: Mathematical descriptions of opacity (http://en.wikipedia.org/wiki/Mathematical_descriptions_of_opacity)