Refraction Formula For Thin Lens

[UchihaClan13]

I was browsing about my optics books,completing numericals and stuff
When I found a a statement called different lens formulas
It had 2 formulas
One,called the thin lens formula or rather the geometric sign convention formula was called 1/v-1/u=1/f(Symbols have their usual meanings) and another one called the virtual-real sign convention formula which was 1/v+1/u=1/f
I know that for a thin lens 1/S0 +1/SI=1/F
Where S0,SI are the object and image distances respectively
So is the statement correct
Or is it just one formula made into two because of the Cartesian SIgn Convention?
Some insight is much appreciated
Thanks!

 

[BvU]

Both are 'correct'. See Hyperphysics where they tell you all the details.

And yes, the Cartesian sign convention flips the sign.

(But now I am personally confused by the minus sign for f in the second link . Anyone ? )

perhaps this helps ?

 

[UchihaClan13]

It helped quite a lot
But my question is why are there 2 lens equations to begin with
I personally use the gaussian formula with sign convention
I never really have used the real-virtual one

 

[BvU]

Same here. But the link reveals that

form using the Cartesian sign convention is often used in more advanced texts because of advantages with multiple-lens systems and more complex optical instruments.