Magnification

Magnification is the ratio of an image’s apparent or measured size to an object’s actual size. It can describe visual enlargement or a measurable scale factor.

Angular magnification: The ratio of the angle subtended by an image viewed through an instrument to the angle subtended by the object viewed unaided. It describes enlargement by visual angle, the relevant measure for telescopes and simple magnifiers.
Similar triangles: Triangles with equal corresponding angles and proportional corresponding side lengths. Optical magnification often follows from proportional sides in ray diagrams.
Microscope: An instrument that uses lenses or other imaging components to produce enlarged views of small objects. Microscopes combine objective and eyepiece magnification to inspect structures beyond unaided vision.
Optical resolution: The ability of an imaging system to distinguish nearby points or fine structures as separate. Magnification enlarges an image; resolution determines whether enlargement reveals distinct detail.
Linear magnification: The ratio of an image’s linear dimension to the corresponding object dimension. It captures enlargement as a direct size ratio rather than a viewing-angle ratio.
Visual angle: The angle an object’s image subtends at an observer’s eye. Apparent size depends on visual angle, not physical size alone.
Telescope: An instrument that collects light from distant objects and forms images for observation or recording. Its angular magnification compares apparent viewing angles with and without the instrument.
Resolving power: The ability of an instrument to distinguish small differences in position, wavelength, or other measured properties. A larger image is not necessarily more informative if the instrument cannot resolve finer structure.
Thin lens equation: An equation relating an ideal thin lens’s focal length, object distance, and image distance. Together with image geometry, it determines the size and orientation of a lens-formed image.
Real image: An image formed where light rays actually converge, so it can be projected onto a surface. Its measurable dimensions can be compared directly with the object’s dimensions.

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