# How to find the magnification

1. Mar 28, 2007

### Aikenfan

1. The problem statement, all variables and given/known data

2. Relevant equations
I am unsure of how to find the magnification:
i know the formula is I/O

3. The attempt at a solution

2. Mar 28, 2007

### Dart82

3. Mar 29, 2007

### Aikenfan

1 / f = 1 / do + 1 / di where f = 13.8 cm and do = 27.6 cm
i get: 27.6, but the computer tells me that it is incorrect...

Last edited: Mar 29, 2007
4. Mar 29, 2007

### Aikenfan

Does anyone know what am doing wrong?

5. Mar 29, 2007

### hage567

This is not correct for finding the magnification.
You were correct when you said M=image height/object height. Magnification can also be expressed in terms of the object distance and image distance (you get this by geometry). So M=-q/p, where q is the image distance and p is the object distance. See if that helps.

6. Mar 29, 2007

### Aikenfan

so the image distance is 27.6 and the object distance is 27.6 as well, so would it be 27.6/27.6

7. Mar 29, 2007

### hage567

Watch out for your signs. The equation has a negative sign in front of it. So if both p and q are positive, your magnification will be negative. Do you know what that means?

8. Mar 29, 2007

### Aikenfan

so the answer would be -1

Last edited: Mar 29, 2007
9. Mar 29, 2007

### Aikenfan

Would that be correct?

10. Mar 29, 2007