Magnifying glass

A magnifying glass is a handheld convex lens that makes nearby objects appear larger when viewed through it. Its short focal length produces an enlarged virtual image when the object is held within the focal distance.

Convex lens: A lens thicker at its center than at its edges that converges parallel light rays. The magnifying glass is a handheld use of this lens shape.
Refraction: The change in direction of light as it passes between materials with different refractive indices. Refraction bends rays through the glass and makes the enlarged image possible.
Loupe: A small high-power magnifier used close to the eye for examining fine detail. A loupe is a compact, specialized form of handheld magnifier.
Magnifying glass history: The development of handheld convex lenses as tools for enlarging nearby objects. Its history traces how a simple lens became a common instrument.
Compound microscope: An instrument that uses multiple lenses to produce highly magnified images of small objects. Unlike a magnifying glass, it combines objective and eyepiece lenses for much greater magnification.
Virtual image: An image formed where diverging light rays appear to originate, rather than where they actually meet. A magnifying glass produces an upright virtual image when the object lies inside its focal distance.
Optical power: A measure of a lens’s ability to converge or diverge light, equal to the reciprocal of focal length in meters. A magnifying glass’s optical power indicates how strongly it bends light.
Watchmaker: A craftsperson who assembles, repairs, and adjusts watches and clocks. Watchmakers use small magnifiers to inspect tiny components and mechanisms.
Roman glass: Glass produced in the Roman world, including vessels and objects with varied optical properties. Ancient glass objects have sometimes been discussed as possible early magnifiers.
Telescope: An optical instrument that gathers light to make distant objects appear closer or larger. A telescope is designed for distant targets, while a magnifying glass is used at close range.

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