# Convex Mirrors and Magnification

kc262

## 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:

Mentor
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?

kc262
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 And because of this discrepancy, I am unsure of how to find the magnification.

Staff Emeritus
Homework Helper
Is the image real or virtual? (And therefore, is the image distance positive or negative?)

Mentor
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