[paul.fr]

A terrific question by Neil, http://www.thenakedscientists.com/forum/index.php?topic=9636.0
made me think of this. Have you seen those doors that automatically frost when you close them, but become clear when you open / unlock the door. How does that work?

[DoctorBeaver]

Polarisation.

Next question.  []

[neilep]

Polarisation.

Next question.  []

What have polar bears got to do with it ?..that is what  "Polarisation" means yes ?...something to do with Polar bears !! ??

[DoctorBeaver]

Polarisation.

Next question.  []

What have polar bears got to do with it ?..that is what  "Polarisation" means yes ?...something to do with Polar bears !! ??

[paul.fr]

Polarisation.

Next question.  []

Eastern europeans, come over here and messing with my glass. Solidarity, my ***

[DoctorBeaver]

When they buy glass they pay by Czech.

[JimBob]

Dear Uncle Chumly,

You know how much I love you, how when we snuggle those two big front teeth make me feel soooo safe that no wolf will ever get me and that when we go swimmin' I love it when you let me ride on your flat tail.

But now you have me confused. Over here in America (I miss you sooo much) when we have doors like the nice guy Paul talked about my friend JimmyB says that they are frosting up or unfrosting - no silly, it isn't like cake frosrting! - because there is this stuff call electricity that makes these itty-bitty things called mollycules that are on the surface, well, they are like soldiers he says, when the electricity calls them to attention they line up and you can see through them but when there is no electricity they do what they want - they make the glass icky and you can't see the other side.

I don't understan. My two bestest friends say it works differently. Please help me understand.

[DoctorBeaver]

Jimbob - What you described is exactly what I meant. Isn't that polarisation? 

[Karen W.]

A terrific question by Neil, http://www.thenakedscientists.com/forum/index.php?topic=9636.0
made me think of this. Have you seen those doors that automatically frost when you close them, but become clear when you open / unlock the door. How does that work?

I have never seen doors like this! Is it new or am I just way in the sticks?

[eric l]

Does that mean that such doors are like the LCD display on my pocket calculator - well, a bit larger maybe ?

[JimBob]

Jimbob - What you described is exactly what I meant. Isn't that polarization? 

I do not believe so. As I understand it, polarization is causing light traveling through a medium leave that medium with their wave-length all fairly well oriented in a single plane. Turning a piece of glass from "clear" to opaque does not cause the wave-lengths to travel in approx. the same planar orientation.

[eric l]

From what I understand - if the doors doe function like the LCD display on my pocket calculator - you have two polarizing filters, but one of them not activated.  This one (crosswise compared to the first) can be activated by an electric current.
Without the current, the molecules are not oriented but at random (as in a liquid), with the current the molecules are oriented (as in a crystal).  Only with the molecules oriented you have the polarization filter effect.
Of course it may also be that without the current none of the filters is active, but with the current both are active and crossed.
Surely someone will soon correct me if I'm wrong.
You can see the effect of crossed polarizing filters if you look at an LCD display through Polaroid sunglasses :  turn the display around and you'll see display - black screen - disoplay - black screen....

[eric l]

It may be that we better forget about polarization in this issue,  the misunderstanding being that an invention of Edwin Land, founder of Polaroid Cy (the instant cameras) is involved.
Just check this on "How Stuff Works" :  http://home.howstuffworks.com/smart-window2.htm

(Only, this does not explain the LCD display turning black when I turn it around in front of my polaroid sunglasses)

[DoctorBeaver]

Jimbob - What you described is exactly what I meant. Isn't that polarization? 

I do not believe so. As I understand it, polarization is causing light traveling through a medium leave that medium with their wave-length all fairly well oriented in a single plane. Turning a piece of glass from "clear" to opaque does not cause the wave-lengths to travel in approx. the same planar orientation.

I thought that when crystals are caused to line up, that was a form of polarisation too. OK, so my terminology was wrong. I apologise.