Re: [Phys-L] lens magnification

[Arlyn DeBruyckere <Arlyn.DeBruyckere@hutch.k12.mn.us>]

di and do change but the ratio stays the same, the magnification and 
focal length stays the same if the materials (not switching from air to 
water for example) stay the same.

On 5/17/13 2:20 PM, Anthony Lapinski wrote:
> I've always wondered about this "simple" idea, and a student just asked
> me. Magnifying glasses (biconvex lenses) are sold with a power rating (3x,
> 4x, etc.). How is this determined? Since m = -di/do, as do changes so does
> di and m.
>
> Is the di somehow a "fixed" value, corresponding to a person's near point?
> And then the object is moved until it's in focus to find the "maximum"
> magnification? If so, the m would change depending on the observer!
>
> Wondering if someone has a simple explanation for this and/or an optics
> demo related to this idea.
>
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