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                                    A convex lens of focal length 40 cm is in contact with a concave lens of focal length 25 cm. The power of the combination isA. `-1.5`dioptersB. `-6.5` dioptersC. `+6.5` dioptersD. `+6.67` diopters | 
                            
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Answer» Correct Answer - A `P=(1)/(f)=(1)/(f_(1))+(1)/(f_(2))=(1)/(0.4)+(1)/(-0.25)=-1.5`diopter.  | 
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