Convex Mirrors and Magnification

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Homework Statement


What is the image distance for an automobile 4.5 m in front of a convex miror with a 0.15 m focal length? I found this to be 0.155 m

The question I'm having a problem with is: What is the magnification?


Homework Equations



magnification = - (image distance/object distance)

The Attempt at a Solution



I thought it would simply be,
-[0.155m/4.5m] = -0.0344. But it's not.

Some help would be much appreciated
 
Last edited:

Answers and Replies

  • #2
Doc Al
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What is the image distance for an automobile 4.5 m in front of a convex miror with a 0.15 m focal length? I found this to be 0.155 m
Careful with signs. For a convex mirror, what sign will the focal length have?
 
  • #3
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Careful with signs. For a convex mirror, what sign will the focal length have?
I realized that because it is a convex mirror, the focal length would be negative. However the marking program marked my answer right. I was confused by this :confused: And because of this discrepancy, I am unsure of how to find the magnification.
 
  • #4
Redbelly98
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Is the image real or virtual? (And therefore, is the image distance positive or negative?)
 
  • #5
Doc Al
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I realized that because it is a convex mirror, the focal length would be negative.
Then how did you get an image distance of +0.155 m ? (See Redbelly98's comment.)
However the marking program marked my answer right. I was confused by this :confused:
Now I'm confused. Your first post seemed to indicate that you knew your answer was wrong.
And because of this discrepancy, I am unsure of how to find the magnification.
You find it just as you stated in your first post:
magnification = - (image distance/object distance)
But you need the correct image distance (correct in both magnitude and sign), of course.
 
  • #6
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ok.. i got it. Turns out there was an error/glitch with the marking program. I got the answer in the end. Thanks for everyone's help! :biggrin:
 

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