Measuring magnification

[hellogreen]

How to Measure magnification
How can I see how strong a magnifying glass is?

I bought this magnifying glass Wholesale Magnifying Glass With Free Shipping From China Distributor and I want
to know how to test it to see how strong it is. I hear a lot of people talk about
magnifying and how strong the magnification is, but I would like to know the true
magnification of my magnifying glass. I have a few of them and some seem stronger then
others. How can I rate these? How can I pin a correct number on mine? How do the companies
that make these come up with these numbers.

[HayZee518]

A dioptre, or diopter, is a unit of measurement of the optical power of a lens or curved mirror, which is equal to the reciprocal of the focal length measured in metres
Convex lenses have positive dioptric value
The dioptre can also be used as a measurement of curvature equal to the reciprocal of the radius measured in metres. For example, a circle with a radius of 1/2 metre has a curvature of 2 dioptres. If the curvature of a surface of a lens is C and the index of refraction is n, the focusing power is ɸ = (n − 1)C. If both surfaces of the lens are curved, consider their curvatures as positive toward the lens and add them. This will give approximately the right result, as long as the thickness of the lens is much less than the radius of curvature of one of the surfaces. For a mirror the focusing power is ɸ = 2C.

[dha]

The real magnification of any object, in terms of size, is really a function of both your glass lens and the lens in your eye. Generally, an object appears larger the closer it gets to your eye. The image size produced upon the retina of your eye is therefore limited by how close the object can be placed in front of your eye and still be in focus. The glass magnifier adds to the focal length of your eye lens allowing an object to be brought closer to your eye and therefore appear larger. A rule of thumb is that the distance of distinct vision, about 10 inches in most people, divided by the focal length of the lens, yields the effective magnification.

So as an example, if the focal length of the lens you have is 1 inch, then you divide 1 inch into 10 inches and the answer is a magnification of 10. Of course there are variations in peoples eyes and their ability to focus at short distances, so this is only a close approximation. The focal length of a lens can be approximated by focusing the image of a distant light bulb, 20 feet away or more, onto a sheet of paper. The distance between the lens and paper at the best focus of the light bulb is the focal length.