Mirror Equation Calculator
The same equation as a thin lens, with the signs read differently, as a real image forms on the same side as the object.
Answer
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Share sends a link that reopens these numbers. Copy details pastes the full breakdown as a list.
Image distance —
Focal length —
Object distance —
Radius of curvature —
Magnification — ×
Image —
The formula
1/f = 1/d₀ + 1/dᵢ f = R ÷ 2 m = −dᵢ ÷ d₀
A spherical mirror and rays close to the axis, using the real-is-positive convention: f is positive for a concave mirror, and dᵢ is positive for a real image in front of the mirror.
What to watch out for
Convex mirrors, with a negative f, always give small, upright, virtual images, which is why they are used for wide views on vehicles.
Frequently Asked Questions
Where is the image in a 10 cm concave mirror at 30 cm?
15 cm in front of the mirror, real and inverted.
What about a convex mirror with f = −10 cm?
An object at 30 cm gives an image 7.5 cm behind it, with a magnification of 0.25.