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प्रश्न
If there is a convex lens of focal length 75 cm and a concave lens of focal length 40 cm, then calculate their combined power and combined focal length.
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उत्तर
Power of convex lens = `100/("f"("cm"))`
= `100/75` = + 1.33 D.
Power of concave lens = `100/("f"("cm"))`
= `100/40` = − 2.5 D.
Their combined power P = + 1.33 D + (− 2.5 D)
P = − 1.17 D.
Their combined focal length F = `100/"P"=100/(-1.17)`
F = − 85.47 cm.
Negative sign indicates that the nature of their combination is concave.
संबंधित प्रश्न
What does sign of power (+ve or –ve) indicate?
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The reciprocal of the focal length in metres gives you the _________ of the lens, which is measured in ___________.
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(a) What is the power of this combination?
(b) What is the focal length of this combination?
(c) Is this combination converging or diverging?
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