how do you find the rough focal length of a convex lens?
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Answer: The rough focal length of a convex lens is obtained by forming sharp image of a very distant object on a screen. The distance of the screen from the lens gives us the rough focal length of the lens.
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The focal length of the lens is the distance between the lens and the image sensor when the subject is in focus, usually stated in millimeters (e.g., 28 mm, 50 mm, or 100 mm). In the case of zoom lenses, both the minimum and maximum focal lengths are stated, for example 18–55 mm.
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To summarize, though, one commonly quoted focal length of the eye is 17mm (this is calculated from the Optometric diopter value). The more commonly accepted value, however, is 22mm to 24mm (calculated from physical refraction in the eye). In certain situations, the focal length may actually be longer.
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To get the binocular-like viewfinder magnification value of a lens, divide the focal length by 50. A formula that is easier (for me at least) to calculate in my head is to divide the focal length by 100 and multiply by 2. Just move the decimal point two places to the left and multiply by 2.
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In photography, the 35 mm equivalent focal length is a measure that indicates the angle of view of a particular combination of a camera lens and film or sensor size. ... Most commonly, the 35 mm equivalent focal length is based on equal diagonal angle of view.
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Determine the focal length of a convex mirror that produces an image that is 16.0 cm behind the mirror when the object is 28.5 cm from the mirror. (Careful: image distances for convex mirrors are always negative.)
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Answer: The focal length of a double convex length is 50 cm. Hence, the focal length of a double convex length is 50 cm.
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A concave lens is thinner in the middle and thicker at the edges. A convex lens is thicker in the middle and thinner at the edges. Used in the camera, focus sunlight, overhead projector, projector microscope, simple telescope, magnifying glasses, etc. It is also used for the correction of the problem in long sight.
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Due to symmetry, there are two principal focus points. Focal length is the distance between the principal focal point and the optical centre of the lens (located on the optical axis and in the "middle of the lens).
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The angle of refraction, and therefore the focal length, will be dependent upon the geometry of the lens surface as well as the material used to construct the lens. Materials with a high index of refraction will have a shorter focal length than those with lower refractive indices.
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Focal length is the distance between the principal focal point and the optical centre of the lens (located on the optical axis and in the "middle of the lens). More focal points could be found on the focus plane, a plane passing through the principal focus point and perpendicular to optical axis.
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For a diverging lens (for example a concave lens), the focal length is negative, and is the distance to the point from which a collimated beam appears to be diverging after passing through the lens. Determining the focal length of a concave lens is somewhat more difficult.
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A plane mirror can be considered as a spherical mirror of infinite radius of curvature. Focal length is half of radius of curvature and hence it is infinity. You can use the mirror formula also to get the focal length of a plane mirror, where the image distance = − object distance.
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The direction of the incident parallel rays and refracted rays in case of convex lens is the same. So, the distance of the point where the incident rays ,after passing through convex lens ,converge which is called focal length of the lens, is positive. ... This means convex lens does converge parallel incident rays.
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The physical properties of a lens at a given focal length also affect the depth of field. A shorter focal length lens (say 27mm) focused at 5 meters, set at f/4 has a deeper DOF (perhaps from 3 meters in front and 20 meters behind) than a longer focal length (say 300mm), also set at f/4 focused at 5 meters.
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Suppose an object is placed u cm in front of a spherical mirror of focal length f such that the image is formed v cm from the mirror, then u, v and f are related by the equation; 1/f= 1/u + 1/v. This equation is referred to as the mirror formula. The formula holds for both concave and convex mirrors.
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The distance from the lens to the focal point is called the focal length. For converging lenses, the focal length is always positive, while diverging lenses always have negative focal lengths. However, these conventions are arbitrary, and physicists could just as easily have made the signs opposite.