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  2. Radius of curvature - Wikipedia

    en.wikipedia.org/wiki/Radius_of_curvature

    Radius of curvature and center of curvature. In differential geometry, the radius of curvature, R, is the reciprocal of the curvature. For a curve, it equals the radius of the circular arc which best approximates the curve at that point. For surfaces, the radius of curvature is the radius of a circle that best fits a normal section or ...

  3. Focal length - Wikipedia

    en.wikipedia.org/wiki/Focal_length

    For a spherically-curved mirror in air, the magnitude of the focal length is equal to the radius of curvature of the mirror divided by two. The focal length is negative for a concave mirror, and positive for a convex mirror. In the sign convention used in optical design, a concave mirror has negative radius of curvature, so

  4. Curvature - Wikipedia

    en.wikipedia.org/wiki/Curvature

    Then the center and the radius of curvature of the curve at P are the center and the radius of the osculating circle. The curvature is the reciprocal of radius of curvature. That is, the curvature is =, where R is the radius of curvature [5] (the whole circle has this curvature, it can be read as turn 2π over the length 2π R). This definition ...

  5. Sagitta (geometry) - Wikipedia

    en.wikipedia.org/wiki/Sagitta_(geometry)

    In the following equations, denotes the sagitta (the depth or height of the arc), equals the radius of the circle, and the length of the chord spanning the base of the arc. As 1 2 l {\displaystyle {\tfrac {1}{2}}l} and r − s {\displaystyle r-s} are two sides of a right triangle with r {\displaystyle r} as the hypotenuse , the Pythagorean ...

  6. Degree of curvature - Wikipedia

    en.wikipedia.org/wiki/Degree_of_curvature

    Where degree of curvature is based on 100 units of arc length, the conversion between degree of curvature and radius is Dr = 18000/π ≈ 5729.57795, where D is degree and r is radius. Since rail routes have very large radii, they are laid out in chords, as the difference to the arc is inconsequential; this made work easier before electronic ...

  7. List of optics equations - Wikipedia

    en.wikipedia.org/wiki/List_of_optics_equations

    Curvature radius of lens/mirror r, R: m [L] Focal length f: m [L] Quantity (common name/s) (Common) symbol/s Defining equation SI units Dimension

  8. Parabola - Wikipedia

    en.wikipedia.org/wiki/Parabola

    The radius of curvature at the origin, which is the vertex of the parabola, is twice the focal length. Corollary A concave mirror that is a small segment of a sphere behaves approximately like a parabolic mirror, focusing parallel light to a point midway between the centre and the surface of the sphere.

  9. Osculating circle - Wikipedia

    en.wikipedia.org/wiki/Osculating_circle

    An osculating circle is a circle that best approximates the curvature of a curve at a specific point. It is tangent to the curve at that point and has the same curvature as the curve at that point. [2] The osculating circle provides a way to understand the local behavior of a curve and is commonly used in differential geometry and calculus.