MAN: Now, this is a spherical lens that's a sphere.
Let's make a spherical lens
which is a section of a sphere but not, in itself, spherical,
and I'll show you how we do that.
We do that with my ring.
I just happen to have this ring.
It's 50 millimeters in diameter.
It's 8 millimeters thick, okay?
And it's made --
This one happens to be made out of a special material.
It's called Monel.
It's a nickel alloy, corrosion-resistant.
And I'm gonna use this to demonstrate spherical lenses
that are both positive lenses and negative lenses --
lenses that have convex surfaces,
lenses that have concave surfaces.
Here we have my ring.
And I'm going to use the two-dimensional beaker.
Got to open up the slit here with my finger
'cause this happens to be a cantankerous bag.
So, I'm sliding --
Okay, so, there.
My two-dimensional beaker is over the ring.
And now I'm gonna pull the two-dimensional beaker off --
also known as a plastic bag -- while I squeeze it,
and I'm gonna put some water on that ring.
Okay, look at that.
Remove a little water.
Oh, look at that.
Oh, perfect.
So, what we have here
is a double-convexed lens.
And this lens is positive.
That means it acts as a magnifier,
and convex means it bulges out, so each side bulges out.
And it's maybe a centimeter,
maybe 10 millimeters, 12 millimeters thick in the center.
And I'm gonna kind of get behind it,
and Andr� told me what I need to do
in order to show magnification.
MAN #2: Great.
MAN #1: Okay.
And this lens,
because it's not a complete sphere,
has fewer aberrations than the lens that was a complete sphere.
This one is still considered a spherical optic
because the surface
is formed in the shape of a spherical surface,
but it's truncated.
It's not a complete sphere, and it has fewer aberrations,
even though it still doesn't make a perfectly fine image.
Okay. How's the ship's log look?
[ Man speaking indistinctly ]
I'm gonna remove more water from this lens
to the point where the meniscus on each side
is almost parallel and the same thickness as the ring.
And look what happens when I do that.
So, I'm sucking out the water with my sponge.
[ Man speaking indistinctly ]
And now I'm just looking at this on the side.
Okay, it looks like the two sides
are pretty much plane-parallel.
And now it's just like a piece of glass.
There's no real magnification in this.
Well, what we're doing now is making a concave lens,
a double-concave lens.
This is referred to as a negative lens.
It makes things smaller instead of bigger.
So, what I'm gonna do now is remove more water
and make this into a negative lens,
where the surfaces are concaved.
And it's concave now because the surface of the water
is pinned to the thickness of this ring,
and I can remove the water,
and the surface is still pinned to this outer edge.
And if I remove water
so that there's less volume in here
than the cylindrical volume of the ring,
the center gets sucked in,
and it makes it into a negative lens.
So, let's see what this looks like now.
Oh, I can tell right now this is a negative lens.
Look at that.
I can see Andr� running the camera, and he is small.
MAN #2: Oh, yeah.
MAN #1: And it's smaller, correct?
MAN #2: Yep.
MAN #1 : Now, there's a whole series of lenses
that are really thin,
and they're called meniscus lenses.
And they're the kind of lenses
that are used to make your eyeglasses.
They're all referred to as meniscus lenses.
But I think this adds a new twist to optical-lens making
because this lens, you can say, is really a meniscus lens.
That concludes our little demonstration
here on the International Space Station,
using water and wire and this little ring
to demonstrate a little bit
about spherical lenses
and spherical lenses that are really not spheres,
but sections of spheres
and what happens with a positive lens that's convexed
and a negative lens that is concaved.
It is good. Okay, so, I'm upside down.
MAN #2: Absolutely.
MAN #1: Okay, now I'm gonna start sucking the water out.
I'm gonna stay in this position.
And we're going from a positive lens into a negative lens.
And now I'm right side up.
MAN #2: Yep.
MAN #1: And I'm smaller -- smaller than life.