1. PF Contest - Win "Conquering the Physics GRE" book! Click Here to Enter
    Dismiss Notice
Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

Mirror questions

  1. May 30, 2005 #1
    I have 2 questions:
    What type and height of image would a rearview mirror produce of a car that was 1.3 m high and 15.0 m behind you, assuming the mirror's radius of curvature is 3.2 m?

    I don't know what equation to use to solve the problem. I think it might be:
    (1/object distance) + (1/image distance) = 1/f

    However, w/ this equation I don't know where to plug in the height (1.3 m). Please help!

    The other question is:
    A mirror at an amusement park shows an upright image of any person who stands 1.3 m in front of it. If the image is three times the person's height, what is the radius of curvature?

    However, I don't understand how to solve it if we don't know how big the image is. I also know that f=r/2, which I might need later on in the problem.

  2. jcsd
  3. May 30, 2005 #2

    Chi Meson

    User Avatar
    Science Advisor
    Homework Helper

    You noticed that f = r/2. You need this for the first question along with the knowledge that the sideview mirror on a car is a diverging mirror. THis means that the focal length must have a negative sign. You have the correct equation, just remember to use a negative focal length.

    There is also the magnification equation which says (h_image / h_object) = (d-image / d_object). You might find this useful for both questions.

    And only a diverging mirror (positive focal length) can create an upright AND larger image.
Know someone interested in this topic? Share this thread via Reddit, Google+, Twitter, or Facebook

Similar Threads - Mirror questions Date
Converging/diverging mirrors/lenses: conceptual question Nov 20, 2016
Convex mirror question Jul 25, 2016
Converging Lens and Plane Mirror Question Nov 20, 2015