I'm getting confused with conventions. I was wondering if this logic is correct:
If an image appears on the same side of an object, then we use a negative focal length for determining information about the image's distance, the possible power, the object's distance, etc.
If an image appears on the opposite side of an object, the focal length is positive.
Under this logic, concave mirrors and diverging lens have negative focal lengths. Is this true?
Also, I think it would be appropriate to assume this is in the context of very rudimentary optics, so the thickness of the lens/mirrors is very small and minuscule in terms of qualitative analysis.