Ill explain atom bombs because h bombs are to long and complicated so I'm using little boy as an example little boy was a gun tipe bomb so you have a metal tube with a solid metal stopper at 1 end and 1 peice of highly enriched uranium on 1 end and 1 on the other on the side without the metal stopper you put conventional explosives behind the uranium block and block it off so when u blowup the tnt the 2 pieces of uranum go flying together in the metal tube the sudden colishion causes a Newton to be relised and I starts a atomic chain reaction of atom splitting that go big boom boom