Power of a lens (P = 1/f (f in metres dioptre))

jee-mainjee-advancedneet-ug

P = 1/f (f in metres dioptre)

What each symbol means

SymbolWhat it stands for
PPower of lens (dioptre, D)
fFocal length in metres (m) — P = 1/f only when f is in m

When to use this

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