Focal length
= Focal length
{title2=$f$}
{wiki}
The focal length measures the focusing power of an <optical lens> or mirror. In a thin converging lens, parallel paraxial rays meet a distance $f$ beyond the lens.
= Focal length
{title2=$f$}
{wiki}
The focal length measures the focusing power of an <optical lens> or mirror. In a thin converging lens, parallel paraxial rays meet a distance $f$ beyond the lens.