# Sign Convention - Physics - Optics

1. Jan 19, 2008

### rajiv_putcha

[SOLVED] Sign Convention - Physics - Optics

I was just looking at some sign conventions and I was wondering if this is true:

Along the principle axis, if Si > 0, then does that mean you have a real, inverted image?

Also along the principle axis, if So < 0, then does that mean you have a virtual, upright image?

2. Jan 19, 2008

### Staff: Mentor

If you're talking about the typical Gaussian sign convention for a thin lens (where the thin lens equation is $1/S_i + 1/S_o = 1/f$) and a typical real object (So > 0), then yes.

Assuming you meant Si < 0 (and with the above caveats), then yes again.

3. Jan 20, 2008

thanks alot!