a so-called virtual object
question: If the object distance is negative then what kind of object does the lens see?, context: Using a positive lens of focal length f, a virtual image results when S1 < f, the lens thus being used a magnifying glass (rather than if S1 >> f as for a camera). Using a negative lens (f < 0) with a real object (S1 > 0) can only produce a virtual image (S2 < 0), according to the above formula. It is also possible for the object distance S1 to be negative, in which case the lens sees a so-called virtual object. This happens when the lens is inserted into a converging beam (being focused by a previous lens) before the location of its real image. In that case even a negative lens can project a real image, as is done by a Barlow lens.
If the object distance is negative then what kind of object does the lens see?
It is also possible for the object distance S1 to be negative, in which case the lens sees a so-called virtual object .
Using a positive lens of focal length f, a virtual image results when S1 < f, the lens thus being used a magnifying glass (rather than if S1 >> f as for a camera). Using a negative lens (f < 0) with a real object (S1 > 0) can only produce a virtual image (S2 < 0), according to the above formula. It is also possible for the object distance S1 to be negative, in which case the lens sees a so-called virtual object. This happens when the lens is inserted into a converging beam (being focused by a previous lens) before the location of its real image. In that case even a negative lens can project a real image, as is done by a Barlow lens.
It is also possible for the object distance S1 to be negative, in which case the lens sees <hl> a so-called virtual object <hl> .
Using a positive lens of focal length f, a virtual image results when S1 < f, the lens thus being used a magnifying glass (rather than if S1 >> f as for a camera). Using a negative lens (f < 0) with a real object (S1 > 0) can only produce a virtual image (S2 < 0), according to the above formula. It is also possible for the object distance S1 to be negative, in which case the lens sees <hl> a so-called virtual object <hl>. This happens when the lens is inserted into a converging beam (being focused by a previous lens) before the location of its real image. In that case even a negative lens can project a real image, as is done by a Barlow lens.
Using a positive lens of focal length f, a virtual image results when S1 < f, the lens thus being used a magnifying glass (rather than if S1 >> f as for a camera). Using a negative lens (f < 0) with a real object (S1 > 0) can only produce a virtual image (S2 < 0), according to the above formula. <hl> It is also possible for the object distance S1 to be negative, in which case the lens sees a so-called virtual object . <hl> This happens when the lens is inserted into a converging beam (being focused by a previous lens) before the location of its real image. In that case even a negative lens can project a real image, as is done by a Barlow lens.