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Apoint - like object is placed at 40 cm distance from a covex lens of 20 cm . Plan mirror is placed behindconvex lens at 30 cm . Find the image distance by this combination. |
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Answer» Solution :Think only convex lens `thereforeu =-40 cm f = +20cm ` `therefore` From lens FORMULA. `1/f = 1/v - 1/u` `therefore1/v = 1/f + 1/u` `therefore 1/v = 1/20 + 1/(-40) = (2-1)/(40) = 1/40` `thereforev =+ 40 cm ` If there is no plane mirror, then image Q. will be at 40 cm from lens. It will work as object for plane mirror. `therefore ` Here, THEDISTANCE of Q. from mirror = 40 - 30 = 10 cm Hence, image will be obtained at 10 cm to left from plane mirror. |
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