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Why Cannot Steel be See through?
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Question:
Here is one that I have been trying to explain for some time but have
be unable to find a satisfactory answer: What makes something transparent?
I understand about the index of refraction, however, it seems
me that if a substance such as silicon can be made into transparent
glass, and a substance like petroleum can be made into transparent
plastic, and so on, it stands to reason that something like steel
could be made transparent as well. Why cannot aluminum be ma transparent,
ala Scotty in Star Trek IV?
Replies:
The main reason is the electrons. The electrons in a metal, which
give it its electrical conductivity, cause the light to be reflected.
Aluminum oxide can be transparent, aluminum can not.
Yup. Glass is not pure silicon, it is silicon di-oxide (a combination
of silicon with oxygen). Plastic not the same material as crude
oil - they have totally changed the chemical composition and carbon
is notorious for being able to do wonderfully different things
in different molecules - Aluminum and other elements just do not
have that ability.
But, so far we have explored only a very limited range of possible
combinations of elements - there are undoubtedly wonderful materials
that could be made in the future. Just think - there are 92 different
elements (that are relatively stable) so the number of materials
with equal parts of just 2 elements is 92^2 = 8464, and you
can try arbitrary combinations of any of them. The total number
even of things in equal combinations would be 2^92 which is
an immensely large number. And then preparation technique
etc all enters in. This is why the whole field of materials
science is so important these days.
Arthur Smith
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Update: June 2012
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