[quote author=dolphin link=topic=439.msg1261#msg1261 date=1172698195]
We put a converging lens and diverging lens in the same stand.We use mesh as an object. when we change the position of lenses there will be different images formed . I want to know what causes the appearance of these several images.

(I hope the information I give is efficient..)
[/quote]

Do you  see many light spots or you see many meshes(images)?
Each hole of mesh is similar to a light source.
For a mesh, you have many light sources(holes), and you will see many light spots.