The focal length of the lens of a simple digital camera is 40 mm, and it is originally focused on a person 25 m away. In what direction must

Question

The focal length of the lens of a simple digital camera is 40 mm, and it is originally focused on a person 25 m away. In what direction must the lens be moved to change the focus of the camera to a person 4.0 m away

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Tryphena 4 years 2021-08-14T18:33:46+00:00 1 Answers 22 views 0

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  1. Helga
    0
    2021-08-14T18:35:44+00:00
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    Answer:

    Explanation:

    Here image distance is fixed .

    In the first case if v be image distance

    1 / v – 1 / -25 = 1 / .05

    1 / v = 1 / .05 – 1 / 25

    = 20 – .04 = 19.96

    v = .0501 m = 5.01 cm

    In the second case

    u = 4 ,

    1 / v – 1 / – 4 = 1 / .05

    1 / v = 20 – 1 / 4 = 19.75

    v = .0506 = 5.06 cm

    So lens must be moved forward by 5.06 – 5.01 =  .05 cm ( away from film )

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