What is the mirror equation?

The mirror equation is 1/f = 1/do + 1/di, where f is focal length, do is object distance, and di is image distance. For a concave mirror f is positive; for a convex mirror f is negative (using the standard sign convention).

What is magnification?

Magnification m = −di/do. A negative m means the image is inverted relative to the object. |m| > 1 means the image is enlarged; |m| < 1 means it is reduced.

What does a negative image distance mean?

A negative image distance (di < 0) means the image is virtual — it forms behind the mirror and cannot be projected onto a screen. Convex mirrors always produce virtual images.

What is the relationship between focal length and radius of curvature?

For a spherical mirror, f = R/2, where R is the radius of curvature. The focal point lies halfway between the mirror surface and the center of curvature.

Can this calculator handle convex mirrors?

Yes. Select "Convex" and the calculator automatically applies a negative focal length in the mirror equation, consistent with the standard real-is-positive sign convention.

Spherical Mirror Calculator

Name: Spherical Mirror Calculator
Availability: InStock
Author: Nham Vu

Solve the mirror equation (1/f = 1/do + 1/di) and find magnification for concave or convex spherical mirrors.

Mirror Parameters

Mirror Type

Concave Convex

Solve For

Unit

Sign Convention

f > 0 — concave mirror (converging)
f < 0 — convex mirror (diverging)
do > 0 — object in front of mirror (real object)
di > 0 — real image (in front of mirror)
di < 0 — virtual image (behind mirror)
m < 0 — inverted image; m > 0 — upright image

Enter values and click Calculate to see results.

Summary

Solve the mirror equation (1/f = 1/do + 1/di) and find magnification for concave or convex spherical mirrors.

How it works

Select the mirror type: concave (converging) or convex (diverging).
Choose which quantity to solve for: image distance, object distance, or focal length.
Enter the two known values with their units.
Click Calculate to apply the mirror equation 1/f = 1/do + 1/di.
Review the result including magnification, image orientation, and image type.

Use cases

Solve optics homework problems involving concave or convex mirrors.
Find the focal length of an unknown mirror from measured object and image distances.
Determine where an image forms for a given object position and mirror.
Check whether an image is real or virtual, upright or inverted, enlarged or reduced.
Verify lab measurements in a physics optics experiment.
Understand how rear-view (convex) mirrors and concave makeup mirrors work.

Frequently Asked Questions

Last updated: 2026-06-11 · Reviewed by Nham Vu