Convex Lens: 10 cm Focal Length, Object at 30 cm
A convex lens with f = 10 cm forms a real image at 15 cm when the object is placed 30 cm away.
How to use this tool
- Enter focal length f, object distance dₒ and image distance dᵢ in the fields above.
- Results update instantly as you type — or click Calculate.
- Read your image distance dᵢ and the full breakdown beneath it.
With the object at three times the focal length, the image forms at 15 cm on the other side — a real, inverted, diminished image.
Frequently asked questions
- What is the sign convention?
- Using the standard convention: distances are positive on the same side as the outgoing light (real image), negative on the same side as the incoming light (virtual image). Converging lenses have f > 0; diverging lenses f < 0.
- What happens when the object is at the focal point?
- The image distance becomes infinite (parallel outgoing rays) — no focused image forms.