Question

A convex lens of focal length 40 cm is in contact with a concave lens of focal length 25 cm. The power of he combination, is :

A
+6.67D
B
6.5D
C
1.5D
D
+6.5D
Solution
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Given,

f1=+40cm

f2=25cm

Power, P=1f

The power of combination,

P=1f1+1f2

P=100+40cm+10025cm

P=1.5D

The correct option is C.

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