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Photograph of the ground are taken form an air-craft ,flying at an altitude of 2000 m by a camera with a lens of focal length `50 cm`. The size of the film in the camera is `18xx18cm`.What area of the ground can be photography by this camera at any one time.A. `720 m xx 720 m`B. `240 m xx 240 m`C. `1080 m xx 1080 m`D. `100 m xx 100 m` |
Answer» Correct Answer - C As ground is at very large distance from camera, thereofore image of ground can be assumed to be formed at the focus of the camera lens. `:. V = 50 m = 0.5 m, u = - 3km = - 3000 m`. If `x` is length of ground photographed, then `|m|= |(h_(i))/(h_(0))| = |(v_(0))/(u)|` or `(0.18)/(x) = (0.5)/(3000)` `:. x = (3000 xx 0.8)/(0.5) = 1080 m` `:.` Area of ground photographed `= 1080 m xx 1080 m` |
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