Use a radioactive eyepiece!

The Kodak Ektamate and Ektar lenses all use thorium glass. Pretty
harmless just sitting around but I wouldn't want to press my eye to
one for any length of time.

http://www.surplusshed.com/pages/item/l3759.html

On Jan 30, 5:22*pm, RichA wrote:
The Kodak Ektamate and Ektar lenses all use thorium glass. *Pretty
harmless just sitting around but I wouldn't want to press my eye to
one for any length of time.

http://www.surplusshed.com/pages/item/l3759.html

There once were some World War II lenses that used radioactive glass,
but that is long gone. Any surplus from the days of digital Group III
fax machines would not use lenses made from that kind of glass -
because the glass isn't made any more.

John Savard

On 31/01/2013 00:22, RichA wrote:
The Kodak Ektamate and Ektar lenses all use thorium glass. Pretty
harmless just sitting around but I wouldn't want to press my eye to
one for any length of time.

http://www.surplusshed.com/pages/item/l3759.html

The half life of natural Thorium 232 is 3x the age of the Earth and
something similar for Lanthanum 138 rare earth glasses. The only worry
with the latter is that uranium was often present as an impurity.

--
Regards,
Martin Brown

On Jan 31, 12:20*am, Martin Brown
wrote:
On 31/01/2013 00:22, RichA wrote:

The Kodak Ektamate and Ektar lenses all use thorium glass. *Pretty
harmless just sitting around but I wouldn't want to press my eye to
one for any length of time.

http://www.surplusshed.com/pages/item/l3759.html

The half life of natural Thorium 232 is 3x the age of the Earth and
something similar for Lanthanum 138 rare earth glasses. The only worry
with the latter is that uranium was often present as an impurity.

--
Regards,
Martin Brown

A banana offers a thousand times as much radiation as any thorium
glass.

On Jan 31, 8:42*am, Brad Guth wrote:
On Jan 31, 12:20*am, Martin Brown
wrote:

On 31/01/2013 00:22, RichA wrote:

The Kodak Ektamate and Ektar lenses all use thorium glass. *Pretty
harmless just sitting around but I wouldn't want to press my eye to
one for any length of time.

http://www.surplusshed.com/pages/item/l3759.html

The half life of natural Thorium 232 is 3x the age of the Earth and
something similar for Lanthanum 138 rare earth glasses. The only worry
with the latter is that uranium was often present as an impurity.

--
Regards,
Martin Brown

A banana offers a thousand times as much radiation as any thorium
glass.

Uh, no. The amount of potassium 40 in the banana is FAR lower than
the (up to 40% of thorium oxide) in the lens.

On Jan 30, 10:46*pm, Quadibloc wrote:
On Jan 30, 5:22*pm, RichA wrote:

The Kodak Ektamate and Ektar lenses all use thorium glass. *Pretty
harmless just sitting around but I wouldn't want to press my eye to
one for any length of time.

http://www.surplusshed.com/pages/item/l3759.html

There once were some World War II lenses that used radioactive glass,
but that is long gone. Any surplus from the days of digital Group III
fax machines would not use lenses made from that kind of glass -
because the glass isn't made any more.

John Savard

I've got the same kind of lens (different focal length, same
dimensions) and it is radioactive. Unless they had fax machines in
WW2...

On Wed, 30 Jan 2013 16:22:32 -0800 (PST), RichA
wrote:

The Kodak Ektamate and Ektar lenses all use thorium glass. Pretty
harmless just sitting around but I wouldn't want to press my eye to
one for any length of time.

http://www.surplusshed.com/pages/item/l3759.html


Might shoot your eye out.

On 01/02/2013 04:35, RichA wrote:
On Jan 31, 8:42 am, Brad Guth wrote:
On Jan 31, 12:20 am, Martin Brown
wrote:

On 31/01/2013 00:22, RichA wrote:

The Kodak Ektamate and Ektar lenses all use thorium glass. Pretty
harmless just sitting around but I wouldn't want to press my eye to
one for any length of time.

http://www.surplusshed.com/pages/item/l3759.html

The half life of natural Thorium 232 is 3x the age of the Earth and
something similar for Lanthanum 138 rare earth glasses. The only worry
with the latter is that uranium was often present as an impurity.


A banana offers a thousand times as much radiation as any thorium
glass.

Uh, no. The amount of potassium 40 in the banana is FAR lower than
the (up to 40% of thorium oxide) in the lens.

I hate to agree with the Venusatic but he is closer than you are to the
truth. Assuming that the banana and thorium glass have equal weight.

Banana K40 0.01% half life 1.25 x 10^9 = 32 Bq
Eyepiece Th232 40% half life 1.4 x 10^10 = 1.7 Bq

There is 4000x more thorium but it is approx exp(12).40/232 times less
radioactive per unit mass = 160,000 x 5.8 = 944,000

So although there is 4000x more thorium the thorium itself provides only
1/230 th of the dose from the banana. The faster decaying daughter
nucleides are responsible for the rest which is another factor of 12 in
output down to stable Pb208 (and fast enough to ignore half lives).

So the ball park numbers for the eyepiece vs the banana is that weight
for weight the banana is 20x more radioactive than the eyepiece. But K40
is an 90% beta and 10% gamma emitter doing little real damage.

However, the eyepiece emits much more damaging alpha particles and by a
happy coincidence that Q factor for radiation damage is 20.

So in terms of biological damage the eyepiece and the banana are
probably about equal. Old uranium glass is more impressively radioactive
even though the amount used to colour it is much smaller.

I wouldn't worry about using the eyepiece or eating a banana either.

--
Regards,
Martin Brown

On Feb 1, 2:53*am, Martin Brown
wrote:
On 01/02/2013 04:35, RichA wrote:









On Jan 31, 8:42 am, Brad Guth wrote:
On Jan 31, 12:20 am, Martin Brown
wrote:

On 31/01/2013 00:22, RichA wrote:

The Kodak Ektamate and Ektar lenses all use thorium glass. *Pretty
harmless just sitting around but I wouldn't want to press my eye to
one for any length of time.

http://www.surplusshed.com/pages/item/l3759.html

The half life of natural Thorium 232 is 3x the age of the Earth and
something similar for Lanthanum 138 rare earth glasses. The only worry
with the latter is that uranium was often present as an impurity.

A banana offers a thousand times as much radiation as any thorium
glass.

Uh, no. *The amount of potassium 40 in the banana is FAR lower than
the (up to 40% of thorium oxide) in *the lens.

I hate to agree with the Venusatic but he is closer than you are to the
truth. Assuming that the banana and thorium glass have equal weight.

Banana * * K40 0.01% half life 1.25 x 10^9 *= 32 Bq
Eyepiece * Th232 40% half life 1.4 x 10^10 *= 1.7 Bq

There is 4000x more thorium but it is approx exp(12).40/232 times less
radioactive per unit mass = 160,000 x 5.8 = 944,000

So although there is 4000x more thorium the thorium itself provides only
1/230 th of the dose from the banana. The faster decaying daughter
nucleides are responsible for the rest which is another factor of 12 in
output down to stable Pb208 (and fast enough to ignore half lives).

So the ball park numbers for the eyepiece vs the banana is that weight
for weight the banana is 20x more radioactive than the eyepiece. But K40
is an 90% beta and 10% gamma emitter doing little real damage.

However, the eyepiece emits much more damaging alpha particles and by a
happy coincidence that Q factor for radiation damage is 20.

So in terms of biological damage the eyepiece and the banana are
probably about equal. Old uranium glass is more impressively radioactive
even though the amount used to colour it is much smaller.

I wouldn't worry about using the eyepiece or eating a banana either.

--
Regards,
Martin Brown

Except you ingest the banana. If the Thorium is mainly an alpha
emitter and it is in an interior lens then the radiation will not
reach the eye.

http://www.richardfisher.com

On Jan 31, 8:35*pm, RichA wrote:
On Jan 31, 8:42*am, Brad Guth wrote:









On Jan 31, 12:20*am, Martin Brown
wrote:

On 31/01/2013 00:22, RichA wrote:

The Kodak Ektamate and Ektar lenses all use thorium glass. *Pretty
harmless just sitting around but I wouldn't want to press my eye to
one for any length of time.

http://www.surplusshed.com/pages/item/l3759.html

The half life of natural Thorium 232 is 3x the age of the Earth and
something similar for Lanthanum 138 rare earth glasses. The only worry
with the latter is that uranium was often present as an impurity.

--
Regards,
Martin Brown

A banana offers a thousand times as much radiation as any thorium
glass.

Uh, no. *The amount of potassium 40 in the banana is FAR lower than
the (up to 40% of thorium oxide) in *the lens.

A half gram of potassium 40 stuck up against your eyeball would not be
such a good idea. Thorium is essentially inert unless it's getting
externally nailed by protons or otherwise activated. It takes a
sphere of roughly 6 foot diameter of pure thorium in order to even
sustain itself.