Question 1

What is the focal length? Thank you.

Accepted Answer

The groove pitch is 0.5mm. The focal length is 320mm

Question 2

Cant I cut this into a smaller sizes with an exacto knife or box cutter?

Accepted Answer

Wow, a bunch of wrong answers. Not only is it possible to trim the edges and use the center portion, it is even possible to cut it into sections, and each section will continue to function. The only difference is that a lens cut from a location not in the center will need to be held over to one side. If it isn't apparent what the total effect will be, just imagine that you took the lens and covered half of it with paper and tape, and then covered have of the remaining rectangular piece, so that once again you have a square section. Obviously this section has to be held to one side, and it probably wouldn't work very well for a reading lens. But you certainly could still use it to start a fire.

Question 3

what is the magnification

Accepted Answer

Unlike with a telescope or a microscope, a magnifying lens's magnification varies as you move closer to or farther from the object you are observing.  I can tell you that it can project the light from the sun to a point about 1/2" in diameter.  This is a concentration, compared to the size of the rectangular lens, of almost a factor of 500.  That doesn't mean that you can see somethings 500 times its size by looking through the lens.  What is means is that it has a huge amount of light gathering surface and focuses it on a very small spot.  This may not be the answer you are looking for; but I can't think of a better way of stating it.  It can ignite a fire in a second or so.

Question 4

How can it be used for 'do it yourself solar cooking'?would this size be bigenough to cook?wouln't it need reflector to reflect to the bottom of pan?

Accepted Answer

I have seen a fresnel lens used to cook (at burning man). They pointed the beam at a cast iron and cast iron pans are good at dispersing the heat evenly across the pan. It probably took a while for it to heat up but it was definitely working.

ASIN	B00IITFX02
Are Batteries Required	No
Best Sellers Rank	#158,722 in Health ( See Top 100 in Health ) #388 in Reading Aids & Magnifiers
Brand Name	Cz Garden Supply
Color	1pack
Customer Reviews	4.4 4.4 out of 5 stars (1,263)
Global Trade Identification Number	00805731900243
Handle Material	Pvc
Item Dimensions L x W	29.8L x 21.1W centimeters
Item Weight	0.11 Pounds
Lens Material	Polyvinyl Chloride (PVC)
Magnification Strength	3 x
Manufacturer	Cz Garden Supply
Manufacturer Part Number	CzFLA4-1
Model Number	CzFLA4-1
Number of Items	1
Number of Packs	1
UPC	805731900243 805731900991
Unit Count	1.0 Count

Cz Garden Supply 8.3" x 11.75" LARGE 3X Fresnel Lens FULL PAGE Magnifier - Solar Oven/DIY Projection TV PLANS (1 pack PREMIUM GRADE Large Lens)

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