Optics Question: Object Distance with a Slit and Lens

[Oerg]

Homework Statement

If I have a light source and a lens then I would take the object distance to be the distance between the center of the lens and the light source. But if I were to place a slit between the light source and the lens, would the object distance now be the distance between the slit and the center of the lens?

I think the object distance would change as the light diffracts out from the slit.

 

[Redbelly98]

But if I were to place a slit between the light source and the lens, would the object distance now be the distance between the slit and the center of the lens?

Yes; the slit may be considered to be a light source in that situation.

 

[nlightner]

I would say that the object distance is the distance between the object and the lens, regardless of whether there is a slit in between. The slit may affect the path of the light rays, causing diffraction, but it does not change the distance between the object and the lens. The object distance is an important parameter in determining the focal length of the lens and the resulting image formation. The presence of a slit may affect the quality of the image formed, but it does not change the fundamental concept of object distance.