Magnification of a mirror
Intermediate
Ratio of image to object height.
m = −v/um = h'/h = −v/u. |m| > 1 enlarged, negative means inverted.
Object at 2f gives m = −1.
Real images are inverted, virtual are upright.
In more detail
The magnification of a mirror is m = −v/u, showing whether the image is larger or smaller and whether it is upright or inverted. A negative value means the image is inverted.
Real-world uses
- Make-up mirrors magnify the face when held close.
- Telescope designers set mirror magnification for field of view.
- Dentists use a concave mirror to magnify a tooth, which is a magnification set by the ratio of image and object distances.
Open the interactive lesson, with simulation and quiz →
Frequently asked questions
What does a positive magnification mean?
The image is upright, as for a convex mirror or a concave mirror with the object inside the focal length.
How do I find the image size?
Multiply the object size by the magnification.
What does a negative magnification mean?
The image is inverted, which is typical for a real image formed by a concave mirror.
Related topics in Optics
Plane mirrors · Spherical mirrors · Mirror equation · Focal length and radius · Refraction of light · Refractive index