Quick Physics Question!

Cosmic.Postman

Explain the significance of conjugate foci.

This came up on a mock a few years back and I can't find a definite answer anywhere....care to help?

finality

I have no idea what that is. I seriously doubt something like that would be asked on a real paper.

Chuchoter

Some of those physics mocks are mad, but if they are what I think they are, its something to do with 1/f1 + 1/f2 = 1/f

Astrozombies

as in.. focal lengths of lenses/mirrors?
probably just like complex conjuates in maths (-1/2i , +1/2i) hmm, dunno, bit of a weirrrrd one.

ride-the-spiral

Conjugate foci
Since the lens equation (1/f = 1/u + 1/v) is symmetrical for image and object, it follows that the positions of an object and its real image can be interchanged. In other words, if an object at some position O produces a real image at I, then if the object is placed at I, the image will be formed at O. Such positions are called conjugate foci. The distance D between the two position is a minimum when u = v, and this occurs when u = 2f.

Stolen from skoool.ie

I doubt this would come up, it's a bit of an awkward definition. It may have come up more on the old course, as I know optics was done a bit more in depth back then. You had to know how a microscope worked and image formation for a system of lenses, perhaps its more important there.#

The current syllabus doesn't specify that it's to be known.