Optics
Mirror Equation
Relates focal length to object and image distances for spherical mirrors.
Variables
fm
Focal length
dom
Object distance
dim
Image distance
Derivation
Derived using similar triangles formed by rays reflecting off a curved mirror surface.
Your notes
0/5000
Check value
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- do = 2 m (Object distance)
- di = 3 m (Image distance)
Result: f = 1.2 m
Other optics formulas with the same quantities
- Thin Lens Equation (Lenses) shares Focal length, Object distance, Image distance
- Lens Magnification (Lenses) shares Image distance, Object distance
- Spherical Mirror Focal Length (Reflection) shares Focal length
- Lensmaker's Equation (Lenses) shares Focal length
- Lens Power (Lenses) shares Focal length
- F-Number (f-stop) (Optical Instruments) shares Focal length
Where this formula is listed
- Optics formulas, under Reflection, alongside Law of Reflection and Fresnel Reflection (Normal Incidence).
- In the optics list it comes after Law of Reflection and before Mirror Magnification.
- Optics formula sheet, one of 34 formulas printed with symbol keys and SI units.
- The full formula index, grouped by category and topic.
Common questions
What is the Mirror Equation formula?
Mirror Equation is written 1/f = 1/d_o + 1/d_i. Relates focal length to object and image distances for spherical mirrors. It belongs to Optics, under Reflection.
What are the units in 1/f = 1/d_o + 1/d_i?
In SI units, f is focal length, measured in m; d_o is object distance, measured in m; d_i is image distance, measured in m.
How is the Mirror Equation formula derived?
Derived using similar triangles formed by rays reflecting off a curved mirror surface. The result is 1/f = 1/d_o + 1/d_i.