Is it possible to create a fire using glasses?

Question

I know that if you position a magnifying glass into the direction of the sun's rays that you can create fire onto an object. Would the same be possible with glasses. I'm just curious because if it could, wouldn't it be dangerous for people wearing glasses in daylight when it is sunny outside.

Could the effect be created with contact lenses too. I don't want to burn my eyes!

Answer 1

I had to ask my friend an optimetrist about this and this is in basic terms.Because of the way the lenses are directed they wont burn your eyes. When you flip them forward like they are on your head it had a cone shape that makes the light shine on one spot but when you look at the sun the light gets dispersed and it wont burn your eyes.

Answer 2

It depends on the lenses: some are convex and some are concave. This determines how they bend light rays, either to a real focus or to a virtual focus (in front of the lens). If there is a real focus, you can get the magnifying glass effect.



However, the point of wearing glasses (or contact lenses) is to make corrections to the way light comes into the eye. Believe it or not, this correction is very small. So, even with lens that could act as a 'magnifying glass', the focal point (where the burning would start) is quite a distance away, and hence the lenses are very safe to wear. You're more in danger from them is they get broken than you are in getting 'flamed' from them.

Answer 3

I suspect that most glasses are too small to start a fire, even on a very sunny day with very flammable material. Certainly contacts would be. That trick only seems to work in movies.



You would need convex lenses, like reading glasses or for far-sighted people, and as others have said the focal point is way further away than your eye so the extra concentration of light while wearing the glasses normally is minimal.



However ... if you are really short-sighted and look into a laser, the light will not focus properly to a point. If you wear corrective glasses, and do it, the laser will focus to a point and is more likely to damage your eye.

Answer 4

Start A Fire With Glasses

Answer 5

Glasses come in two types, positive and negative diopter. +diopter is like a magnifying glass, a small one. You could use this to focus light onto a small spot. But I don't think it will get hot enough to start a fire. Perhaps.



The other type of lens, more common, disperses light instead of concentrating it.

Answer 6

Looking at the sun is a no-no,but ordinary spectacles will not make things worse.

.If you look directly at the sun the retina's will have a fine needle point burned area which will be small but permanent.further such episodes will be cumulative.Whether you wear spectacle or use binoculars will not change the issue by much.it will depend on the collecting area for the radiated energy(so spec's and binoculars could concentrate more energy in the focal area).An astronomical telescope will barbecue you retina's in a flash.

Answer 7

No...



The focus of eye glasses is way too far away...