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Homework Help: Why doesn't this formula seem to work with convex mirrors? or did i miss somthing?

  1. Mar 14, 2006 #1
    Hello everyone, I seem to be getting all the mirrors right that where concave but now i have a convex one and it doesn't seem to be working when im' finding the image distance and magnification/properties.

    Here is the problem:
    Heres my work: both the i and the m where wrong, i also tried postive values for the i and it was also wrong.
    http://suprfile.com/src/1/69p5rx/lastscan.jpg [Broken]

    I did get the last part of the question right though, i said it was going to be
    upright, behind the mirror and virtual
    Last edited by a moderator: May 2, 2017
  2. jcsd
  3. Mar 14, 2006 #2


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    First off, you haven't drawn a picture! Ray diagrams are very useful in these types of problems. The tricky part of lenses is making sure that all your signs are correct. For this type of mirror, I believe the focal length is negative. Do you understand what the difference is between a real and a virtual image? Do you understand what is meant by the focal length? The diagram will be helpful. Draw a convex mirror with an object in front, then draw the light-rays coming off the object and see where they go after bouncing off the mirror. Plugging and chugging won't help you understand the concepts, and a good understanding of the concepts is the key to tricky test questions.
  4. Mar 14, 2006 #3
    Thanks again Eep! I forgot all about convex mirros, the focal length is always negative u treat it as a diverging lens i guess! It wokred! wee!
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