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In an optical bench experiment to measure the focal length of a concave mirror random error in focal length will beA. minimum when `u = f` and maximum when `u= infty`B. minimum when `u = infty` and minimum when `u = f`C. minimum when `u= 0` and maximum when `u= 2f`D. minimum when `u = 2f` and maximum when `u =0` |
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Answer» Correct Answer - D `(Deltaf)/f^(2)=(Deltau)/u^(2)+(Deltav)/v^(2) Deltau=Deltav` for optical bench ` Rightarrow 1/(f^(2))xxd(Deltaf)=Deltau[-2/u^(3)-2/v^(3)xx(dv)/(du)]_(for min error)=0` ` (dv)/(du)=-v^(3)/u^(3)=-v^(2)/u^(2)Rightarrow v=u` ` for `u = 2f`, error is min |
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