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A lens with one convex and one concave side is convex-concave or meniscus. Convex-concave lenses are most commonly used in corrective lenses, since the shape minimizes some aberrations. For a biconvex or plano-convex lens in a lower-index medium, a collimated beam of light passing through the lens converges to a spot (a focus) behind
Thin lenses produce focal points on either side that can be modeled using the lensmaker's equation. [5] In general, two types of lenses exist: convex lenses, which cause parallel light rays to converge, and concave lenses, which cause parallel light rays to diverge. The detailed prediction of how images are produced by these lenses can be made ...
In geometrical optics, light is considered to travel in straight lines, while in physical optics, light is considered as an electromagnetic wave. Geometrical optics can be viewed as an approximation of physical optics that applies when the wavelength of the light used is much smaller than the size of the optical elements in the system being ...
The focal point F and focal length f of a positive (convex) lens, a negative (concave) lens, a concave mirror, and a convex mirror.. The focal length of an optical system is a measure of how strongly the system converges or diverges light; it is the inverse of the system's optical power.
These lenses have a direct counterpart in visible light. The saw-tooth lens is a unique optical scheme suggested and demonstrated by Cederstrom. [6] It approximates a parabolic lens much as a numerical computation on a grid approximates a smooth line, with a series of prisms that each deflect the X-rays over a minute angle.
Bottom: The formation of a real image using a concave mirror. In both diagrams, f is the focal point, O is the object, and I is the image. Solid blue lines indicate light rays. It can be seen that the image is formed by actual light rays and thus can form a visible image on a screen placed at the position of the image.
The basic scheme is that the primary light-gathering element, the objective (1) (the convex lens or concave mirror used to gather the incoming light), focuses that light from the distant object (4) to a focal plane where it forms a real image (5). This image may be recorded or viewed through an eyepiece (2), which acts like a magnifying glass.
Modern improvements typically have fields of view of 60°−70°. König design revisions use exotic glass and / or add more lens groups; the most typical adaptation is to add a simple positive, concave-convex lens before the doublet, with the concave face towards the light source and the convex surface facing the doublet.