magnification glass

[zavor]

hello all, i have a question , maybe is stupid but i'am no such a laser expert.
I wondering how mw woul be the light of the sun trougt a magnfication glass, the classic leaf-ant burning that i think all of use tried as little child. If can burn so easy i think it's a lot of mw, so it is safe to starring at the dot close as we did in childhood ?

Thanks

 

[Deleted member 8382]

This was oncecalculated. Get the average sun radiation, it will be a xx Watt/square meter number.

Then calcluate the ammount of power that goes in your magnifing glass (depends onthe size) and there you have it!

 

[Ways]

In the southern UK the amount of solar energy measured at ground level varies from around 400 W/m2 in mid winter to around 1200 W/m2 in mid summer, hmmm with figures like those i might sack my lasers and get a magnifying glass with an area of 1 square meter and some B movie / alien hybrid ants to fry , oh and muscles like schwarzenegger in his prime cos thats gotta be one heavy lump of glass

As to staring at the dot (its been a while) i seem to remember it being rather bright, perhaps a decent pair of sunglasses would be enough and assuming the above theoretical magnifying glass... factor 50k sunscreen!

 

[rocketparrotlet]

Ways: We all float down here...

--

Anyway, you can buy a fresnel lens on Ebay, they have a lot of power and they're not too heavy. Fairly inexpensive as well.

If your magnifying glass has an area of 1/100m^2, which sounds reasonable, with a solar radiation of 1,000W/m^2, then the dot would be 10W. This definitely has potential to damage your eyes, however, not as much as a laser; it is not coherent light. Sunglasses are probably recommended though.

-Mark

 

[Deleted member 8382]

I think last time it was calculated they said something about the glass looses as well as the fact that a lot of light is not focused (if it were it would be completly dark right under the glass), I think they said something about 1-2W in ideal conditions.

yours,
Albert

 

[tatman]

I got a fresnel lens off the front of a projection-type big screen talevision. It will start a fire with wood within 3 seconds on a sunny day and even when it's overcast it don't take long. I can honestly say that it is scarey. I make sure I don't even store it near a window.

 

[diachi]

In the southern UK the amount of solar energy measured at ground level varies from around 400 W/m2 in mid winter to around 1200 W/m2 in mid summer, hmmm with figures like those i might sack my lasers and get a magnifying glass with an area of 1 square meter and some B movie / alien hybrid ants to fry , oh and muscles like schwarzenegger in his prime cos thats gotta be one heavy lump of glass

As to staring at the dot (its been a while) i seem to remember it being rather bright, perhaps a decent pair of sunglasses would be enough and assuming the above theoretical magnifying glass... factor 50k sunscreen!

1200W/M2 Somehow that doesn't seem accurate ... I've got a Fresnel lens thats about 1/4M2 ... that means it outputs close to 300W! I'm sorry but that would be enough to engrave steel!

EDIT:

Wait ... 0.25*0.25 = 0.0625M , which would equal 25W

 

[pseudolobster]

http://en.wikipedia.org/wiki/Solar_radiation#Solar_constant

Outside of the atmosphere, the total energy delivered to earth by the sun is 1,366W/m^2.. Not all of that is visible light, and not all of that makes its way through the atmosphere, but roughly 1kW/m^2 is what's generally accepted as average.