I have various magnifying glasses and I'm using them when I take macro photos with a phone or a camera. I want to group/label my magnifying glasses by their magnification power. And by magnification power I mean something like 10x.
To calculate their magnification power, I've read several Wikipedia pages, Lens (Optics) for calculating focal length, and Magnification for calculating magnification power, but I end up with wrong results. I must be doing something wrong.
For example, I have this biconvex magnifying glass
Some of its properties
diameter = 6 cm
thickness at the edge = 3 mm
thickness at the center = 7 mm
radius of the curvature = 225 mm (1)
I figured the focal length of magnifying glass by experimenting with a light source, but I want to calculate it on a paper.
How can I calculate the focal length of a magnifying glass and its magnification power?
For example, in this page Amazon - SE Folding Pocket Magnifier, it says 10x for the magnifier.
How do the companies that produce magnifying glasses calculate it?
I'd appreciate if you could provide an example calculation in your answer, preferably with the values I've given.
(1) I didn't calculate it, I just drew the magnifying glass in Illustrator with its actual values
Index of refraction doesn't matter. The result doesn't have to be 100% correct. 1.52 can be used as the index.