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Class X Sciences [papers from previous years] To determine focal length of a concave mirror a student obtains the image of a well lit distant object on a screen. To determine the focal length of the given concave mirror he needs to measure the distance between: (A) mirror and the object (B) mirror and the screen (C) screen and the object (D) screen and the object and also mirror and the screen |
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Answer» tance between the pole of the mirror and the image of a distant object is called the focal length of the concave mirror.1/f = 1/ u + 1/V for a mirror.If the object is distant, u >> f or u >> v. so 1/u << 1/v or 1/f.so we IGNORE it. 1/f = 1/v => f = v.v is the distance between the mirror and the screen.u = distance between the mirror and the object.f = focal length of the mirror. |
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