Mirror formula (1/f = 1/v + 1/u)

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1/f = 1/v + 1/u

What each symbol means

SymbolWhat it stands for
fFocal length of mirror (Cartesian sign convention) (m)
uObject distance from pole (m)
vImage distance from pole (m)

When to use this

Standard JEE / NCERT assumptions unless stated (paraxial, thin lens, coherent YDSE sources, etc.).