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Homework Help: Convex mirror question

  1. Mar 24, 2008 #1
    I'm really bad at physics and am quite lost on a homework assignment of mine. Any help that I can get would be fantastic, thanks.

    1. The problem statement, all variables and given/known data
    A concave mirror has a radius of curvature of 60 cm. Calculate the image position and magnification of an object placed in front of the mirror at distances of (a) 90 cm and (b) 20 cm. (c) Draw ray diagrams to obtain the image in each case.

    2. Relevant equations

    Not sure of any relevant equations.

    3. The attempt at a solution

    I actually don't know much about this particular subject but in my attempt to draw some ray diagrams I assumed the real image would be magnified as smaller than the object. Also I think that the image is directly behind the lens the same distance as the object is in front of the mirror. So for example for a. the image would be 90 cm behind the lens. I don't really want answers so much as I would like to see if I'm doing something wrong, because I feel that I am.
  2. jcsd
  3. Mar 24, 2008 #2
    The focal length is one half of the radius. You are given the object distance. You are asked to find the image distance. You have a formula that relates the focal length, the image distance, and the object distance. Plug numbers in.

    The magnification is the ratio of the image height to the object height. You have a formula that relates that to the image distance and the object distance. Plug numbers in.

    To draw the ray diagram, you have a list of rules for what would happen when rays reflect from the mirror, assuming that each of the incident rays was traveling in a specific direction, such as parallel to the principal axis, or through a focus, etc.
  4. Mar 24, 2008 #3
    Thank you, though you keep saying "I have the formula", I don't think I do... In any case however, I understand
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