InterviewSolution
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InterviewSolution
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It is desired to make an achromatic combination of two lenses, `(L_(1)& L_(2))` made of materials having dispersive power `omega_(1)` and `omega_(2)(ltomega_(1))`. If the combination of lenses is converging then:A. `L_(1)` is convergingB. `L_(2)`is convergingC. Power of `L_(1)`is greater than the power of `L_(2)`D. None of these |
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Answer» Correct Answer - B Condition for achromatism `(omega_(1))/(f_(1))+(omega_(2))/(f_(2))=0` `(omega_(1))/(omega_(2))=-(f_(1))/(f_(2))` Given that`omega_(1)gtomega_(2)` `(omega_(1))/(omega_(2))gt1` `-(f_(1))/(f_(2))gt1` `f_(1)gtf_(2)`and of opposite nature So,`P_(1) ltP_(2)`For focal length of combination `(1)/(f)=(1)/(f_(1))+(1)/(f_(2))` `P=P_(1)+P_(2)` Since the combination of lens is converging that means `Pgt0`,,So power of`L_(2)` must be greater & must be positive .option (B)is correct choice. |
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