The maximum magnification formula for a stand magnifier uses F as the dioptric power. What is F in this context?

• A. Dioptric power of the magnifying lens
• B. Focal length of the stand
• C. Object distance
• D. Eyepiece power

Answer: (A)

In this context, F represents the dioptric power of the magnifying lens. Dioptric power is the reciprocal of the focal length (in meters) and is measured in diopters. It tells you how strongly the lens bends light: a shorter focal length means a higher dioptric power and greater magnification. The stand itself doesn’t contribute optical power, so F comes from the magnifying lens. Eyepiece power or the stand’s focal length aren’t what this formula uses to define F.