Magnifying Glass Magnification

M = 1 + \frac{D}{f}

The angular magnification of a simple magnifying glass when the image is at the near point (25 cm). For relaxed viewing at infinity, M = D/f.

Variables

Angular magnification

unitless

Near point distance (typically 25 cm)

Focal length of magnifier

Derivation

Derived by comparing the angle subtended by the image through the magnifier to the angle subtended by the object at the near point without the magnifier.

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