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A burning apparatus consisting of two biconvex lens. A lens is a transmissive optical device that focuses or disperses a light beam by means of refraction.A simple lens consists of a single piece of transparent material, while a compound lens consists of several simple lenses (elements), usually arranged along a common axis.
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Esotropia (from Greek eso 'inward' and trope 'a turning' [1]) is a form of strabismus in which one or both eyes turn inward. The condition can be constantly present, or occur intermittently, and can give the affected individual a "cross-eyed" appearance. [2]
The Canon EF 28–90mm f / 4–5.6 is a full frame SLR zoom lens, also often included as a kit lens with Canon EOS film cameras. The maximum aperture is f / 4 at 28mm, reducing to f / 5.6 at 90mm. When set to 90mm, this will create a moderate amount of background blur for portrait photography.
The EF 28mm lenses are a group of prime lenses made by Canon that share the same focal length. These lenses use the EF type mount that fits the Canon EOS line of cameras. When used on a camera body with an APS-C sensor, such as the Canon EOS 700D , it provides a narrower field of view, equivalent to a 45 mm lens mounted on a 35 mm frame body.
Illustration of the relationship between optical power in dioptres and focal length in metres. A dioptre (British spelling) or diopter (American spelling), symbol dpt, is a unit of measurement with dimension of reciprocal length, equivalent to one reciprocal metre, 1 dpt = 1 m −1.
Uses an equiconvex crown glass lens (i.e. R 1 > 0 with −R 1 = R 2) and a complementary-curved second flint glass lens (with R 3 = R 2). The back of the flint glass lens is flat ( R 4 = ∞). A Littrow doublet can produce a ghost image between R 2 and R 3 because the lens surfaces of the two lenses have the same radii.
8×42 roof prism binoculars with rainguard and opened tethered lens caps. Binoculars or field glasses are two refracting telescopes mounted side-by-side and aligned to point in the same direction, allowing the viewer to use both eyes (binocular vision) when viewing distant objects.