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Re: Cartesian Sign Convention for Optics



My suggestion is to use the same convention as in their textbook.
Otherwise you will create unneeded confusion. I usually spend
some time to show that conventions are arbitrary.

One possibility is to keep all distances positive. But then you no
longer have one thin lens formula for all possible locations of
objects. You have several similar formulas, sometimes with +
and sometimes with - in front of the 1/s1, 1/s2 or 1/f terms.
Conventions are introduced to allow a single formula.
Ludwik Kowalski

On Friday, Mar 28, 2003, at 12:28 US/Eastern, Tina Fanetti wrote:

How many of you use the Cartesian sign convention for optics?
I am used to the sign convention that has virtual images being
negative and object distances being positive.

I am wondering which to use with my calculus physics students.
Their book uses the Cartesian sign convention....