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(a) A convex lens of focal length 25 cm and a concave lens of focal length 10 cm areplaced in close contact with one another: (i) What is the power of this combination? (ii) What is the focal length of this combination? (iii) Is this combination converging or diverging? |
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Answer» Answer: Answer f 1
=25cm=0.25m P 1
= f 1
1
= 0.25 1
=4D f 2
=−10cm=−0.1m P 2
= f 2
1
= −0.1 1
=−10D (a) Power of the COMBINATION : P=P 1
+P 2
=4D+(−10D) =−6D (b) Focal length of the combination: f= P 1
= −6 1
=−0.1666m=−16.66cm (c) The combination has negative focal length , so it is DIVERGING. |
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