An eye specialist prescribes spectacles having a combination of a convex lens of focal length 40cm in contact with a concave lens of focal length 25cm. The power of this lens combination in Dioptre is:
A
−1.5
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B
+1.5
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C
+6.67
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D
−6.67
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Solution
The correct option is A−1.5 Focal length of convex mirror, f1=+40cm
Focal length of concave mirror, f2=−25cm