InterviewSolution
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InterviewSolution
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A diminished image of an object is to be obtained on a screen 1.0 m from it. This can be achieved by appropriately placingA. a concave mirror of suitable focal lengthB. a convex mirror of suitable focal lengthC. a convex lens of focal length less than 0.25 mD. a concave lens of suitable focal length |
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Answer» Correct Answer - C NOTE: A convex mirror and a concave lens always produce virtual image. Therefore, option (b) and (d) are not correct. The image by a convex lens is diminished when the object is placed beyond 2f. Let`u=2f+x` Using `(1)/(v)-(1)/(u)=(1)/(f)` `implies (1)/(v)-(1)/(-(2f+x)=(1)/(f)` `(1)/(v)=(1)/(f)+(1)/(2f+x)=(2f+x-f)/(f(2f+x)=((f+x))/(f(2f+x)` But `u+v=1`(given) `(2f+x)+(f(2f+x))/(f+x)le1` `2f+x[1+(f)/(f+x)]le1` `implies ((2f+x))^2/(f+x) le1` `implies (2f+x)^2lef+x. The above is true for `flt 0.25 m`. |
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