How to Calculate Mirror Equation
What is Mirror Equation?
Mirror equation relates object distance, image distance, and mirror radius of curvature. It applies to both concave and convex mirrors, predicting image formation.
Formula
The calculator applies 1/f = 1/s_o + 1/s_i where f = R/2
- R
- R value — Variable used in the calculation
- f
- 1/s_o + 1/s_i where f = R/2 — 1/s_o + 1/s_i where f = R/2
Step-by-Step Guide
- 1Enter object distance and mirror radius, or two distances
- 2The calculator applies 1/f = 1/s_o + 1/s_i where f = R/2
- 3Results show image location, size, and orientation
Worked Examples
Input
s_o = 20 cm, R = 30 cm
Result
s_i = 60 cm, magnification = 3×
Real inverted magnified image
Common Mistakes to Avoid
- ✕Using the wrong sign conventions for concave vs. convex mirrors
- ✕Assuming magnification directly relates to focal length
Frequently Asked Questions
Why is focal length half the radius of curvature?
For a spherical mirror, the focal point is at the geometric center, halfway between vertex and center of curvature.
What images do convex mirrors form?
Convex mirrors always form virtual, upright, diminished images. This is why they're used for wide-angle car mirrors.
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