# Optics problem

1. Aug 16, 2009

### jsalapide

Where do you put an object in front of a concave mirror of focal length 10 cm to produce an image that is inverted and 2.5 times greater than the object?

I have no idea how to solve this.. help..

2. Aug 16, 2009

### Staff: Mentor

What are the basic equations describing spherical mirrors and image formation?

3. Aug 16, 2009

### jsalapide

i only know the equation on how to solve for the focal length

f= (pq)/(p+q)

where p is the distance of the object from the mirror and q as the distance of the image from the mirror.

4. Aug 16, 2009

### Staff: Mentor

Good. And how does image size relate to p and q?

5. Aug 16, 2009

### jsalapide

i come to think of it, the image size does not change no matter what value of p and q is.

could that mean that there is no way that the image will be 2.5 times greater than the object?

6. Aug 16, 2009

### Staff: Mentor

You'd better check that assumption. As you move the object around, the position and size of the image will change.