Convex lens

A lens thicker at its center than at its edges that bends parallel incoming light rays toward a focal point. Its converging action depends on its shape and the refractive indices of the lens and surrounding medium.

Refraction: The change in direction of a wave as it passes between materials with different propagation speeds. A convex lens converges light by refracting rays at its two surfaces.
Optical axis: The reference line passing through the centers of curvature of an optical system's surfaces. The lens's principal focus and symmetric ray diagrams are defined relative to this line.
Magnifying glass: A simple optical instrument that uses a convex lens to produce an enlarged virtual image. It uses a convex lens with the object inside the focal length.
Concave lens: A lens thinner at its center than at its edges that makes parallel rays diverge. It produces the opposite ray behavior from a convex lens in air.
Focal length: The distance from a lens or mirror to its principal focus. It measures how strongly the convex lens converges parallel rays.
Principal focus: The point where rays parallel to an optical system's axis converge, or appear to diverge from. Parallel rays entering a convex lens meet at its principal focus.
Camera lens: An optical assembly that focuses light to record an image on a sensor or film. Convex elements help a camera lens focus real images onto its image plane.
Plano-convex lens: A converging lens with one flat surface and one outward-curved surface. It is a specific convex-lens design used when one curved surface is sufficient.
Thin lens equation: An equation relating an optical element's focal length, object distance, and image distance. It predicts image location from the lens's focal length and object position.
Refractive index: A measure of how much light slows in a material compared with its speed in vacuum. The lens material's index relative to its surroundings helps set its converging strength.

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