Relates the focal length of a lens to the object distance and the image distance.
Symbols
f
focal length
[m]
x
object distance
[m]
y
image distance
[m]
Where it comes from
Relates the focal length of a lens to the object and image distances. The signs of the quantities depend on the type of lens and on whether the image is real or virtual.
When to use it
Image construction in lenses; camera, eye, magnifying glass.
Example
A lens with a focal length of 0.2 m, an object at a distance of 0.5 m. Calculate the image distance.