A convex lens of focal length 40 cm is kept in contact with a concave lens of focal length 25 cm. The power of the combination is
Text Solution
Verified by ExpertsThe correct answer is:
C
power of convex lens
p 1 = 
D = 
= 2.5 D
power of concave lens
p 2 = 
D = – 4D
∴ power of combination (in contact)
p = p 1 + p 2 = + 2.5 D – 4D = – 1.5D
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