How it works
For the real-is-positive thin-lens convention, 1/f = 1/object distance + 1/image distance.
Input definitions
- Signed focal length (m)
- Enter the value in the labeled unit.
- Object distance from lens (m)
- Enter the value in the labeled unit.
A worked example
- Signed focal length (m)
- 0.1
- Object distance from lens (m)
- 0.3
Assumptions & limits
Ideal educational model in the stated SI units. Real equipment, structural design and safety decisions need appropriate professional analysis; losses are excluded unless entered.
Sources & review
Maintained by AnsRio. Methods and examples use automated checks; this does not imply independent professional certification.
Method updated 2026-10-18. Content checked against the stated method and examples. Our verification approach.
Common questions
What does a negative image distance mean?
It denotes a virtual image on the object side under this sign convention. The thin-lens approximation excludes lens thickness and aberration.
How does Thin lens image distance work?
For the real-is-positive thin-lens convention, 1/f = 1/object distance + 1/image distance.
What should I check before using Thin lens image distance?
Ideal educational model in the stated SI units. Real equipment, structural design and safety decisions need appropriate professional analysis; losses are excluded unless entered.