1.

A convex lens of focal length 40 cm is in contact with a concave lens of focal length 25 cm. The power of the combination isA. `+1.5`B. `-1.5`C. `+6.67`D. `-6.67`

Answer» Correct Answer - B
Power of convex lens `P_(1)=(100)/(40)=2.5D`
Power of concave lens `P_(2)=-(100)/(25)=-4D`
Now `P=P_(1)+P_(2)=2.5D-4D=-1.5D`


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