Thin-lens image equation
A paraxial lens relates object and image distances.
Key knowledge
In thin-lens paraxial optics with the same surrounding medium on both sides, 1/f = 1/d_o + 1/d_i using a consistent real-is-positive convention.
Values and equations
1/f = 1/d_o + 1/d_i
- f
- Signed focal length m
- d_o
- Signed object distance m
- d_i
- Signed image distance m
Conditions and scope
- For a real object d_o > 0; d_i > 0 for a real image opposite the object and < 0 for a virtual image.
- f > 0 for converging and < 0 for diverging lenses; thick lenses and large-angle aberrations are excluded.
Sources · 1
References
Sources retain their recorded scope. A source link alone does not establish verification of every statement.
Evidence and review
Equation 2.19, derivation approximation and sign conventions.
2026-10-10 · Thin paraxial lens equation only; no all-rays perfect-focus assertion.
Entry details
Permanent link to this entry ↗- Record identity
- physics-thin-lens
- Revision
- university-reference.1
- Structured reference record
- University reference · University core expansion