| Topic: |
Science > Physics |
| User: |
"Robert11" |
| Date: |
01 Mar 2004 05:40:37 PM |
| Object: |
Green Color On Glass Edge ? |
Hello:
Always wondered about this.
I have a glass coffee table.
When looking perpendicular to the surface, it really looks clear; no
discernable green tint.
But, looking along an edge, it looks very green.
Also, and this is really important I think, if one looks along the edge, but
caddy-corner, (in other words, just thru
a very small length or portion) it still looks very greenish.
Actually if you look along the edge thru the whole length of the glass slab,
or into an edge and then right out again thru a very small length of glass
edge, e.g., a corner, it looks just as green.
Why ?
Why isn't it also green looking thru a "thick" piece of glass, as well as an
edge ?
Seems to be independent of the distance one looks thru, other than entering
thru an edge of the plate.
I believe, but am not certain, that if one would look thru a small glass
sphere, it would Not look green. True ?
I'm not looking for an explanation of the green color, which I assume is
due mainly to Na ion absorption (true?), but for an explanation as to why
it's clear in one direction, and
green in the edge viewing direction
Thanks,
R.obert
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| User: "" |
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| Title: Re: Green Color On Glass Edge ? |
03 Mar 2004 12:49:56 PM |
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"Robert11" <rgsxrose@comcast.net> wrote in message
news:AMednV-rnpXpVN7dRVn-uQ@comcast.com...
Hello:
Always wondered about this.
I have a glass coffee table.
When looking perpendicular to the surface, it really looks clear; no
discernable green tint.
But, looking along an edge, it looks very green.
Also, and this is really important I think, if one looks along the edge,
but
caddy-corner, (in other words, just thru
a very small length or portion) it still looks very greenish.
Actually if you look along the edge thru the whole length of the glass
slab,
or into an edge and then right out again thru a very small length of glass
edge, e.g., a corner, it looks just as green.
Why ?
Why isn't it also green looking thru a "thick" piece of glass, as well as
an
edge ?
Seems to be independent of the distance one looks thru, other than
entering
thru an edge of the plate.
I believe, but am not certain, that if one would look thru a small glass
sphere, it would Not look green. True ?
I'm not looking for an explanation of the green color, which I assume is
due mainly to Na ion absorption (true?), but for an explanation as to why
it's clear in one direction, and
green in the edge viewing direction
Total internal reflection in a long multi path path length.
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| User: "Franz Heymann" |
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| Title: Re: Green Color On Glass Edge ? |
03 Mar 2004 04:08:57 PM |
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"Robert11" <rgsxrose@comcast.net> wrote in message
news:AMednV-rnpXpVN7dRVn-uQ@comcast.com...
I believe, but am not certain, that if one would look thru a small glass
sphere, it would Not look green. True ?
I have some completely clear glass marbles, about 1 cm diameter.
I also have some specimens of glass, with a typical dimension of 2 cm, which
I have cut and polished to illustrate some diamond cuts. They are
completely clear.
[snip]
Franz
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| User: "Uncle Al" |
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| Title: Re: Green Color On Glass Edge ? |
03 Mar 2004 04:45:25 PM |
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Franz Heymann wrote:
"Robert11" <rgsxrose@comcast.net> wrote in message
news:AMednV-rnpXpVN7dRVn-uQ@comcast.com...
I believe, but am not certain, that if one would look thru a small glass
sphere, it would Not look green. True ?
I have some completely clear glass marbles, about 1 cm diameter.
I also have some specimens of glass, with a typical dimension of 2 cm, which
I have cut and polished to illustrate some diamond cuts. They are
completely clear.
It depends on the glass. Compare the cost/weight of marbles and
bottle glass.
--
Uncle Al
http://www.mazepath.com/uncleal/
(Toxic URL! Unsafe for children and most mammals)
"Quis custodiet ipsos custodes?" The Net!
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| User: "" |
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| Title: Re: Green Color On Glass Edge ? |
03 Mar 2004 04:52:19 PM |
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In article <c25l1o$c30$2@hercules.btinternet.com>, "Franz Heymann" <notfranz.heymann@btopenworld.com> writes:
"Robert11" <rgsxrose@comcast.net> wrote in message
news:AMednV-rnpXpVN7dRVn-uQ@comcast.com...
I believe, but am not certain, that if one would look thru a small glass
sphere, it would Not look green. True ?
I have some completely clear glass marbles, about 1 cm diameter.
I also have some specimens of glass, with a typical dimension of 2 cm, which
I have cut and polished to illustrate some diamond cuts. They are
completely clear.
Years ago I visited the Corning glass museum (in Upstate New York,
strongly recommended). Among all other things they've a series of
demos illustrating the properties of various types of glass. One of
the is transparency demo. You've a series of glass cylindrs, about 5
cm diameter, varying lengths, so you can look (along the cylinder
axis) at some pattern on the wall, on the other side. You can see
pretty well through a 5 cm long one, quite poorly through a 10 cm,
pretty much nothing other than a blur through 20. Then, on the side,
you've a similar cylinder, but about 1.5 m long, made from the glass
they use for optical elements. And you look through it and it is
so transparent as if it wasn't there at all.
Mati Meron | "When you argue with a fool,
meron@cars.uchicago.edu | chances are he is doing just the same"
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| User: "Ken Muldrew" |
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| Title: Re: Green Color On Glass Edge ? |
04 Mar 2004 01:03:32 PM |
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wrote:
Years ago I visited the Corning glass museum (in Upstate New York,
strongly recommended).
Seconded.
pretty much nothing other than a blur through 20. Then, on the side,
you've a similar cylinder, but about 1.5 m long, made from the glass
they use for optical elements. And you look through it and it is
so transparent as if it wasn't there at all.
I remember that one as well, although my memory puts it at closer to
10m long.
Ken Muldrew
kmuldrezw@ucalgazry.ca
(remove all letters after y in the alphabet)
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| User: "" |
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| Title: Re: Green Color On Glass Edge ? |
04 Mar 2004 03:17:42 PM |
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In article <40477d40.89194717@news.ucalgary.ca>, (Ken Muldrew) writes:
mmeron@cars3.uchicago.edu wrote:
Years ago I visited the Corning glass museum (in Upstate New York,
strongly recommended).
Seconded.
pretty much nothing other than a blur through 20. Then, on the side,
you've a similar cylinder, but about 1.5 m long, made from the glass
they use for optical elements. And you look through it and it is
so transparent as if it wasn't there at all.
I remember that one as well, although my memory puts it at closer to
10m long.
Well, my numbers are from vague memory too, not exact, and if anything
I preferred to err on the conservative side. Thus, yes, it could be
longer than what I wrote, though I don't think there was room there
for 10 m. But we agree that we're talking about order of magnitude of
meters. Was pretty amazing.
Mati Meron | "When you argue with a fool,
meron@cars.uchicago.edu | chances are he is doing just the same"
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| User: "Jim Deutch" |
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| Title: Re: Green Color On Glass Edge ? |
02 Mar 2004 04:26:37 PM |
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On Mon, 1 Mar 2004 18:40:37 -0500, "Robert11" <rgsxrose@comcast.net>
wrote:
Also, and this is really important I think, if one looks along the edge, but
caddy-corner, (in other words, just thru
a very small length or portion) it still looks very greenish.
You're not really looking through the corner: refraction makes the
light path much longer than you may suspect. Try sending a laser
pointer beam through: you may be able to see what's happening.
Otherwise, just study a bit of geometrical optics.
Jim Deutch
--
I started out with nothing & still have most of it left.
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| User: "Uncle Al" |
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| Title: Re: Green Color On Glass Edge ? |
01 Mar 2004 06:13:14 PM |
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Robert11 wrote:
Hello:
Always wondered about this.
I have a glass coffee table.
When looking perpendicular to the surface, it really looks clear; no
discernable green tint.
But, looking along an edge, it looks very green.
Also, and this is really important I think, if one looks along the edge, but
caddy-corner, (in other words, just thru
a very small length or portion) it still looks very greenish.
Actually if you look along the edge thru the whole length of the glass slab,
or into an edge and then right out again thru a very small length of glass
edge, e.g., a corner, it looks just as green.
Why ?
Why isn't it also green looking thru a "thick" piece of glass, as well as an
edge ?
Seems to be independent of the distance one looks thru, other than entering
thru an edge of the plate.
I believe, but am not certain, that if one would look thru a small glass
sphere, it would Not look green. True ?
I'm not looking for an explanation of the green color, which I assume is
due mainly to Na ion absorption (true?), but for an explanation as to why
it's clear in one direction, and
green in the edge viewing direction
Cheap soda lime glass is contaminated with iron as Fe(+2). Long
pathlengths show a distinct green color. Better soda lime has a trace
of pyrolusite (manganese dioxide) added as a decolorizer. Oxidation
to Fe(+3) gives nearly colorless glass. However, prolonged exposure
to UV in sunlight ("desert glass") or gamma irradiation gives you a
lovely lavender color.
Borosilicate, aluminosilicate, Vycor 96% silica, and fused silica
glasses are all colorless to very large pathlengths for not having
transition metal contamination.
http://www.cmog.org/pdf/aroglass.pdf
2000K download.
--
Uncle Al
http://www.mazepath.com/uncleal/
(Toxic URL! Unsafe for children and most mammals)
"Quis custodiet ipsos custodes?" The Net!
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