Question #3a335
1 Answer
It means the effect is the same even though the physical construction is different. They are "equivalent", not identical.
Explanation:
A very useful and practical application of mathematics to physical properties! A "classical" optics assembly would need certain physical dimensions of a single lens, or a series of lenses. Magnification and focal points were all determined by size and lengths.
Maybe the best practical example of an "equivalent lens" is the Fresnel lens. By taking the geometric dimensions of a solid lens and reducing it to only the effective curved portions, an almost flat, thin sheet of partial sphere curves produces the same magnification as a much larger, heavier and more expensive "standard" lens shape.
Similarly, "equivalent focal length" may be achieved in different dimensions, including some electronic versions. An example may be a multiply-reflecting telescope that reduces the effective length needed for the focal length.
