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Roma Jani
Asked: 2022-11-10T01:51:25+05:30 In:

Two lenses are placed in contact with each other and the focal length of combination is `80 cm`. If the focal length of one is `20 cm`, then the power of the other will be
A. `1.66 D`
B. `4.00 D`
C. `-1.00 D`
D. `-3.75 D`

Two lenses are placed in contact with each other and the focal length of combination is `80 cm`. If the focal length of one is `20 cm`, then the power of the other will be
A. `1.66 D`
B. `4.00 D`
C. `-1.00 D`
D. `-3.75 D`
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1 Answer

  1. Correct Answer – d

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Smriti Thakkar
Asked: 2022-11-07T10:50:57+05:30 In:

Two lenses are placed in contact with each other and the focal length of combination is `80 cm`. If the focal length of one is `20 cm`, then the power of the other will be

Two lenses are placed in contact with each other and the focal length of combination is `80 cm`. If the focal length of one is `20 cm`, then the power of the other will be
Parabola
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1 Answer

  1. Here, `F = 80 cm, f_1 = 20 cm, P_2 = ?`
    `P = (100)/(F) = (100)/(80) = 1.25 D, P_1 = (100)/(f_1) = (100)/(20) = 5 D`
    As `P_1 + P_2 = P :. P_2 = P – P_1 = 1.25 – 5 = -3.75 D`.

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