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Spots asked in Science & MathematicsPhysics · 1 decade ago

Mirrors problem help?

So the problem goes like this:

An object is located 13.5 cm in front of a convex mirror, the image being 7.35 cm behind the mirror. A second object, twice as tall as the first one, is placed in front of the mirror, but at a different location. The image of this second object has the same height as the other image. How far in front of the mirror is the second object located?

I know that the magnification equation is involved, but the thing is that it seems to contradict.

m = hi/ho = -di/do

Based on the problem, the convex mirror's magnification is 7.35/13.5 = 49/90. However, in the other situation, the convex mirros's magnification is 2, which contradicts the 1st magnification.

Can someone tell me what I did wrong and how to solve it please?

1 Answer

Relevance
  • Andres
    Lv 4
    1 decade ago
    Favorite Answer

    Image 1

    Magnification 1= m1 = y1' / y1 = - s1' / s1

    s1 = 13.5cm & s1' = -7.35cm

    m1 = 0.544

    Image 2

    y2 = 2 y1 & y2' = y1

    m2 = y2' / y2 = y1' / 2 y1 = m1 / 2 = - s2' / s2 = 0.2722

    Besides:

    1/s2 + 1/s2' = - 1/focus = 1/s1 - 1/s1'

    s1 = 13.5cm & s1' = 7.35cm

    Then:

    1/s2 + 1/s2' = -0,0619

    - s2' / s2 = 0.2722 --> 1/s2' = - 1 / (.2722 s2)

    1/s2 - 1/ (.2722 s2) = -.0619

    s2 = 43.19cm fron of the mirror- answer -

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