glacier glasses vs. regular sunglasses

[lizard_brain]

Surface reflection information? You mean, the ground?

 

"I'm just checking out the surface reflection information."

 

It's mere sales hype.

[Hugh Conway]

Surface reflection information? You mean, the ground?

 

erm, you aren't getting it are you?

 

no light reflecting from the ground reaching your eyes = no information

 

light reaching eyes = information that your brain processes

[Bigtree]

 

Clipped from Wikipedia for you eggheads (I don't really know what all this stuff means, but I still prefer a polarized lens):

 

"The simplest polarizer in concept is the wire-grid polarizer, which consists of a regular array of fine parallel metallic wires, placed in a plane perpendicular to the incident beam. Electromagnetic waves which have a component of their electric fields aligned parallel to the wires induce the movement of electrons along the length of the wires. Since the electrons are free to move, the polarizer behaves in a similar manner as the surface of a metal when reflecting light; some energy is lost due to Joule heating in the wires, and the rest of the wave is reflected backwards along the incident beam.

 

For waves with electric fields perpendicular to the wires, the electrons cannot move very far across the width of each wire; therefore, little energy is lost or reflected, and the incident wave is able to travel through the grid. Since electric field components parallel to the wires are absorbed or reflected, the transmitted wave has an electric field purely in the direction perpendicular to the wires, and is thus linearly polarized. Simply stated, only light traveling in a certain direction passes through the polarizer, and the rest of the light is absorbed or reflected. Note that the polarization direction is perpendicular to the wires; the concept that waves "slip through" the gaps between the wires is incorrect.

 

For practical use, the separation distance between the wires must be less than the wavelength of the radiation, and the wire width should be a small fraction of this distance. This means that wire-grid polarizers are generally only used for microwaves and for far- and mid-infrared light. Using advanced lithographic techniques, very tight pitch metallic grids can be made which polarize visible light. Since the degree of polarization does little depend on wavelength and angle of incidence, they are used for broad-band applications such as projection.

 

It is interesting to consider why there is a reflected beam, but no transmitted beam, when the symmetry of the problem suggests that the electrons in the wires should re-radiate in all directions. In simple terms the transmitted beam does "exist", but is in exact antiphase with the continuing incident beam, and so "cancels out". This, in turn, seems to contradict the idea that the incoming wave is "driving" the electrons in the wires, and so is "used up" (leaving no continued beam to cancel out the transmitted wave). In fact, if we assume that there is no heating, then no energy is used to drive the electrons — a better mental image is to think of them as "riding" on the waves that result from the interaction.

 

Certain crystals, due to the effects described by crystal optics, show dichroism, a preferential absorption of light which is polarized in a particular direction. They can therefore be used as polarizers. The best known crystal of this type is tourmaline. However, this crystal is seldom used as a polarizer, since the dichroic effect is strongly wavelength dependent and the crystal appears coloured. Herapathite is also dichroic, and is not strongly coloured, but is difficult to grow in large crystals.

 

Polaroid film was in its original form an arrangement of many microscopic herapathite crystals. Its later H-sheet form is rather similar to the wire-grid polarizer. It is made from polyvinyl alcohol (PVA) plastic with an iodine doping. Stretching of the sheet during manufacture ensures that the PVA chains are aligned in one particular direction. Electrons from the iodine dopant are able to travel along the chains, ensuring that light polarized parallel to the chains is absorbed by the sheet; light polarized perpendicularly to the chains is transmitted. The durability and practicality of Polaroid makes it the most common type of polarizer in use, for example for sunglasses, photographic filters, and liquid crystal displays. It is also much cheaper than other types of polarizer.

 

An important modern type of absorptive polarizer is made of elongated silver nanoparticles embedded in glass. These polarizers are more durable and can polarize light much better than Polaroid film, with low absorption of correctly-polarized light. Such glass polarizers are widely used in optical fiber communications. The best known trade names are Polarcor, made by Corning and colorPol, made by Codixx."

 

[tvashtarkatena]

Surface reflection information? You mean, the ground?

 

erm, you aren't getting it are you?

 

no light reflecting from the ground reaching your eyes = no information

 

light reaching eyes = information that your brain processes

 

I'm just not getting any of this. The brilliant light reflecting off of Carl's boundless knowledge of high school introductory physics must be blinding me.

 

His inability to realize that he's the butt of this joke is even more astounding, however. Lecture on, Carl! We are but empty vessels!

Edited January 10, 2008 by tvashtarkatena

[Hugh Conway]

I'm just not getting any of this. The brilliant light reflecting off of Carl's boundless knowledge of high school introductory physics must be blinding me.

 

your condscension cracks me up you lovable fat cunt

[tvashtarkatena]

I am lovable. Ask me Mum.

[tvashtarkatena]

I'm just not getting any of this. The brilliant light reflecting off of Carl's boundless knowledge of high school introductory physics must be blinding me.

 

your condscension cracks me up you lovable fat cunt

 

You misspelled something, Professor.

 

Now, about refraction....

[Figger_Eight]

The important thing is to have coverage all around the eye. Well fitting sport wraps do that just find. Most all good sunglasses block UV rays, but there are just a few that have a visible light transmission percentage in the single digits that I know of: Oakley Black Iridium, Smith has a special order Flash Blue lens and Julbo has one as well. If you're in the snow on a bright sunny day, you might need a lens that dark.

[Figger_Eight]

Polarized Lenses - I'm in the camp that don't like them for the snow. I need all the information I can get so I don't crash into a tree.

[tvashtarkatena]

Polarization filters out trees?

 

 

 

 

 

 

 

Kidding....

[Hugh Conway]

Now, about refraction....

 

n-iK

[Couloir]

This thread is classic cc.com at its best.

[Frikadeller]

All this talk about burning eyeballs by the sun is starting to scare me into wearing this when I ski and climb on snow...

 

 

 

I will probably also save on not using sunscreen on me face either.

[lightning]

I have a POLARIZED pair of smith slider style sunglasses that I use on my road bike.

 

Three lenses: Clear, Amber and dark.

 

I think that I will start using these in all but the brightese of summer snow conditions.

 

Also, I burned my eyes when I was about 12 and they are still sensiative to light, so we will see how this goes.

[Hugh Conway]

I have a POLARIZED pair of smith slider style sunglasses that I use on my road bike.

 

Three lenses: Clear, Amber and dark.

 

I think that I will start using these in all but the brightese of summer snow conditions.

 

only the dark lenses are polarized

[lightning]

I know, but I think that the others will still be usefull in varying lite conditions

[Jens]

I will have to agree. Classic cc!