PHYSICAL QUANTITY

Focal length: formulas and units of measurement

Focal length: symbol F, unit m. Formulas and explanations for Optics.

F

\text{m}

meter

KEY CONNECTIONS

Formulas

\frac{1}{F} = \frac{1}{d} + \frac{1}{f}

1 / F = 1 / d + 1 / f

F = \frac{d f}{d + f}

F = df / (d + f)

D = \frac{1}{F}

D = 1 / F

NOTATION

$F$: Focal length is the distance from the optical center of the lens to its main focus.
$d$: Object distance - the distance from the lens to the object in question.
$f$: Image distance is the distance from the lens to the resulting image.
$D$: Optical power is the ability of a lens to collect or scatter light.

THEORY

PRACTICE