An eye specialist prescribes spectacles having combination of convex lens of focal length 40cm in contact with a concave lens of focal length 25cm. The power of this lens combination in diopters isA. `+1.5 D`B. `-1.5D`C. `+6.67`DD. `-6.67D`

An eye specialist prescribes spectacles having combination of convex l

1.	An eye specialist prescribes spectacles having combination of convex lens of focal length 40cm in contact with a concave lens of focal length 25cm. The power of this lens combination in diopters isA. `+1.5 D`B. `-1.5D`C. `+6.67`DD. `-6.67D`
Answer» Correct Answer - B (b) `therefore` power of the lens=`1/"Focal length"` focal length of combination of convex and cocave lenses is given by `1/F=1/(f_(1))=1/F_(2)` Where, `f_(1)` and `f_(2)` be the focal lengths of convex and concave lenses, respectively Now, `1/F=1/0.4=1/((-0.25))` `1/F=-1.5` Power, P=-1.5D

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An eye specialist prescribes spectacles having combination of convex lens of focal length 40cm in contact with a concave lens of focal length 25cm. The power of this lens combination in diopters isA. `+1.5 D`B. `-1.5D`C. `+6.67`DD. `-6.67D`

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