Thin lens

A thin lens is an optical element whose thickness is negligible relative to its surface curvature radii. Its refraction can therefore be modeled as occurring at a single plane.

Thin lens equation: The relation connecting an ideal thin lens’s focal length, object distance, and image distance. It predicts image position once the lens and object distances are specified.
Refraction: The change in direction of a wave as it passes between media with different wave speeds. A lens focuses light through refraction at its surfaces.
Camera: An optical device that records images by directing light onto a photosensitive sensor or film. Camera designs use lens groups whose image formation is often estimated with thin-lens relations.
Thick lens: A lens whose thickness must be included when calculating its optical behavior. It replaces the single-plane approximation when separation between lens surfaces matters.
Lensmaker's equation: An equation relating a lens’s focal length to its refractive index and surface curvatures. It shows how the thin lens’s material and curved surfaces determine its focal length.
Refractive index: A dimensionless measure of how slowly light propagates in a material relative to vacuum. The index contrast between lens and surroundings controls how strongly the lens bends light.
Eyeglasses: Wearable lenses that alter incoming light to compensate for refractive errors or improve vision. Their corrective power is commonly specified using the thin-lens approximation.
Paraxial approximation: An approximation in which rays remain close to an optical axis and make small angles with it. Thin-lens equations usually assume paraxial rays in addition to negligible lens thickness.
Focal length: The distance from an optical system’s principal plane to its focal point. It measures the focusing strength represented by the thin-lens model.
Radius of curvature: The radius of the sphere that best matches a curved surface at a specified point. The thin-lens approximation compares lens thickness with its surface curvature radii.

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Field of viewRelated: Thin-lens geometry links object distance, image distance, and the extent projected onto an image plane.