A) + 1.5 D
B) ? 2.5 D
C) - 1 D
D) + 1 D
Correct Answer: C
Solution :
Key Idea: Powers of lenses placed in contact are added up. When a convex lens (Power positive) is kept in contact with a concave lens (Power negative), than the power of combination is \[P={{P}_{1}}+{{P}_{2}}\] Given, \[{{P}_{1}}=+1.5\,D,\,{{P}_{2}}=-2.5\,D\] \[P=+1.5-2.5=-1\,D\] Note: Since power is negative combination behaves like a diverging lens.
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