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An eye specialist prescribes spectacles ...

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 is

A

1.5 D

B

`-2.5 D`

C

`-1.5 D`

D

`+2.5 D`

Text Solution

Verified by Experts

The correct Answer is:
C
Power of the convex lens `=(100)/(40)=2.5 D`
Power of the concave lens `=(100)/(-25)=-4D`
`therefore P=P_(1)+P_(2)=(-4+2.5)=-1.5 D`
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