I am having a problem understanding the mathematical reasoning of finding the description of image in convex mirror...(adsbygoogle = window.adsbygoogle || []).push({});

We know the relation,

1/v + 1/u =1/f

is true for all mirrors... we can prove this for both concave and convex mirrors... In case of convex mirrors we use the conventional + and - to get to this general form(I guess real positive system)...

But when they used that formula to find out the position of image they again said for concave mirrors f is minus... I don't understand this point... We derived this formula saying r is minus for concave mirrors... Now what is left is the value... But again why are we saying this is minus? :surprised

I tried solving without taking it to be minus but that leads to false answer... Why? Please explain...

**Physics Forums - The Fusion of Science and Community**

Dismiss Notice

Join Physics Forums Today!

The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

# 1/v + 1/u =1/f

**Physics Forums - The Fusion of Science and Community**