A lens is an optical element that allows for light to pass through it and either _focuses_ or _disperses_ that light. # The geometric structure of lenses ## Radii of curvature # Modeling lenses When modeling lenses we often need to create approximate models of their effect on light that pass through them. Often this means completely ignoring imperfections inherent in manufacturing as well as aspects of their [geometry](Lens.md#The%20geometric%20structure%20of%20lenses) if those aspects are determined to have a small enough effect to not be relevant for a given purpose. ## Thin lens approximation In situations where the radius of curvature is much larger than the lens thickness we model lenses as infinitely [thin](Thin%20lens.md) planes. i.e. we don't always model the propagation of the ray or wave in the distance through the lens. ([... see more](Thin%20lens.md)) ## Thick lenses In modeling a [thick lens](Thick%20lens.md) we need to account for the propagation through the thickness of the lens. This is for situations where the radius of curvature is reasonably close to the distance light propagates through the lens. ([... see more](Thick%20lens.md)) # Lens types * Convex lenses * [[Biconvex lens]] * [[Planoconvex lens]] * Meniscus lenses: * [[Positive meniscus]] * [[Negative menisucs]] * Concave lenses: * [[Biconcave lens]] * [[Planoconcave lens]] #Electromagnetism/Optics #ExperimentalTools/ExperimentalToolsinOptics