a spherical mirror produces a magnification of -1 on a screen placed at a distance of 40cm from the mirror i) write the type of mirror ii) W

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a spherical mirror produces a magnification of -1 on a screen placed at a distance of 40cm from the mirror i) write the type of mirror ii) What is the focal length of the mirror

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Tài Đức 6 months 2021-07-29T02:31:14+00:00 1 Answers 7 views 0

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    2021-07-29T02:32:16+00:00

    Answer:

    f =-20 cm

    Explanation:

    Given that,

    The magnification of a spherical mirror, m = -1

    The image distance, v = 40 cm (for negative magnification)

    The magnification of a concave mirror is negative. The mirror showing -1 magnification is a concave mirror.

    Let f be the focal length of the mirror. We know that,

    m=\dfrac{-v}{u}\\\\-1=\dfrac{-v}{u}\\\\v=u

    Object distance, u = -40 cm

    Using mirror’s formula i.e.

    \dfrac{1}{f}=\dfrac{1}{u}+\dfrac{1}{v}\\\\f=\dfrac{1}{\dfrac{1}{-40}+\dfrac{1}{-40}}\\\\f=-20\ cm

    So, the focal length of the mirror is 20 cm.

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