The optics of lenses?

Question

Where must the object be placed in order to have an inverted image on the opposite side of the lens to the object?

Where must the object be placed to have a virtual erect image?


I can tell you one MIGHT be the focal point, but I truly do not know, please help!

Answer 1

An object at the focal point will form a virtual erect image. This is an image that can be viewed by your eye and appears to be at infinity. This is the type of imaging used in a magnifying glass or a telescope or microscope eyepiece.

Any object beyond the focal point of the lens will form a real, inverted image. The location of the object and its image is given by 1/S1 + 1/S2 = 1/f, where S1 is the object-to-lens distance, S2 is image-to-lens distance, and f is focal length. This is the sort of image formed by a camera lens or the objective lens of a telescope or microscope.

All of this applies to lenses of positive focal length. You can't form a real image with a negative focal length lens.