# Curved Mirrors (concave)

1. May 14, 2006

### mmg0789

how can you tell when the image will become real or virtual in a concave mirror, the distance?..i'm not sure

*edit*
oh i think i know..is it the magnification, if the magnification is more than 1 then that means its virtual since it would be upright and a bigger image

is that right?

Last edited: May 14, 2006
2. May 14, 2006

### Hootenanny

Staff Emeritus
This is correct;
Using the standar equation for a mirror;

$$\frac{1}{d_{O}} + \frac{1}{d_{i}} = \frac{1}{f}$$

When $d_{i}$ is positive, the image is real; if it is negative the image is virtual. $d_{i}$ is the horizontal displacement of the image from the centre of the mirror. $d_{O}$ is the horizontal displacement of the object from the centre of the mirror and $f$ is the focal length of the mirror (which is positive for a concave mirror).

It is possible it have a real image that is larger than the object. What is the definition of a real and virtual image?

http://hyperphysics.phy-astr.gsu.edu/hbase/geoopt/mirray.html#c3

3. May 14, 2006

### arunbg

Actually if the magnification is +ve , the image is virtual.
-ve->real
(As per new Cartesian sign convention)

4. May 14, 2006

### Hootenanny

Staff Emeritus
I agree, that's why I said above
I did forget to mention however, that the image would be inverted.

~H