Magnifying Glass Magnification
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
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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- D = 2 m (Near point distance (typically 25 cm))
- f = 3 m (Focal length of magnifier)
Result: M = 1.6666667
Other optics formulas with the same quantities
- Telescope Magnification (Optical Instruments) shares Angular magnification
Where this formula is listed
- Optics formulas, under Optical Instruments, alongside Numerical Aperture, F-Number (f-stop) and Depth of Field.
- In the optics list it comes after Rayleigh Criterion and before Microscope Magnification.
- Optics formula sheet, one of 34 formulas printed with symbol keys and SI units.
- The full formula index, grouped by category and topic.
Common questions
What is the Magnifying Glass Magnification formula?
Magnifying Glass Magnification is written M = 1 + 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. It belongs to Optics, under Optical Instruments.
What are the units in M = 1 + D/f?
In SI units, M is angular magnification (dimensionless); D is near point distance (typically 25 cm), measured in m; f is focal length of magnifier, measured in m.
How is the Magnifying Glass Magnification formula derived?
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. The result is M = 1 + D/f.