Lighting Messed up with multiple meshes

Hey guys sorry for this probably very noob question. But I just can’t seem to be able to figure it out… whenever I try to put multiple meshes together, like 2 walls, the entire lighting messes up. the light shines through to the other side in the crack (even though I made sure there is no crack) and the shadows are replicated on each new mesh instead of continued from one to the other. Is there a way to set it up so the light will act as if it is 1 mesh or am i going to have to model the entire wall or what ever it may be into 1 giant piece?
I added a screenshot which shows what I mean. Hope to get some help =) [17210-unity+issue.jpg|17210]

I solved this problem this scond becaus i had it too.
first select the prefab in your project window and look in the inspector(model tab)

set normal to “Calculate” and tangents to “Calculate”

that worked for me! Oh I am so happy!