# Calculations with Various Optical Instruments

## Focal Length of a Lense

The focal length f is the distance of a lense (or mirror) to the point where a light source, which is shining through the instrument, is focussed most.

The value of magnification refers to the length, the magnification of a surface area is this value squared (when doubling a surface in each direction, its area gets quadrupled).

Matching websites: Angular Diameter, Photographic Exposure, Convert Length Units, Lens as Geometric Solid

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