Lenses

I just read that a lens can be made from paraffin wax. How is that possible?

And was the first lens used to improve vision or for setting things on fire?

 

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The ancestry of eyeglasses dates back to 4 BC, when people utilized water to magnify items for clearer viewing. The modern framed eyeglasses were known to exist as early as 1285, then referred to as "spectacles". By definition, eyeglasses are devices used to correct impaired vision, be it farsighted or nearsighted. Today, eyeglasses are prescribed lenses fitted on a frame to that rest on the bridge of your nose.

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wouldn't magnification be the vision part? Why make something bigger unless you want to see it better?

 

Was the first lens a glass container of water or a chunk of clear rock like quartz?

 

Some quartz is quite transparent. I have seen a few very good transparent pieces. It can be and has been cut to make lenses, crystal balls, small transparent windows for various uses, and watch crystals. Another term for clear quarts is "rock crystal." The Wikipedia entry for "crystal ball" has a picture of the world's largest flawless crystal ball, weighing 106.75 pounds and measuring 12.9 inches in diameter. Smaller natural crystal balls are still not hard to find. This is just to mention what can be cut from natural rock without melting and reforming. A crystal ball is a sort of lens.

Beryl was an old favorite for crystal balls. Sapphire has seen use in windows for furnaces. Emeralds are fairly transparent and do come in colorless varieties. They are a variety of beryl, actually.

There is also calcite which is transparent but is useless for lenses because it has double refraction.

Fluorite is in use for high-end lenses.

The first lenses may have been as likely to have been made from quartz because it could have been easier to find transparent quartz than transparent man made glass.

 

I looked it up on Google and it seems to be a lens for focusing microwaves, not light. I guess that the wax is able to refract microwaves. It's just the density of the material.

 

I remember in basic microscopy classes we used to put little drops of oil on the end of the objective lens to improve resolution for really tiny stuff - could it be something like that?

 

thanks MetaKron. I was wondering. So its teh density that is needed, not the clarity?

 

To microwaves paraffin wax IS clear. It's the density that is needed, a material with a homogenous density that can be formed into shapes. I would think that they would be able to do this with plastics and glass also.

 

Actually, it's not the density so much as the relative permitivity and permeability of the material. (Essentially how the material reacts to electric and magnetic fields for those who haven't studied Maxwells equations.)

 

so it could be any kind of wax?

 

AFAIK it could be, providing as kevinalm says, it's got the permitivity etc.
And equally AFAIK the only wax that has is... tadaaa paraffin wax.
But always struck me as weird using wax to focus microwaves - you'd think it would just melt

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wow, why doesn't it? Wrong kind of microwaves?

 

The molecules are probably too large to get excited by the unfocused microwaves ?
Microwaves in microwave ovens only excite water molecules.

 

I dunno.
But apparently, (if I read it correctly on a skim) polyethylene can also be used..
http://www.lib.ncsu.edu/theses/available/etd-12182003-180914/unrestricted/etd.pdf

 

so if I put a rock in my microwave, it won't get hot?

 

Unless it has water in it.