Can white light be captured inside an opaque container. If not, why? When the source is disrupted it becomes dark. why?

Theoretically, yes! Unfortunately the container would not only have to be opaque, but a perfect reflector (reflecting 100% of the incident light) on the inside. If the inside was anything less than a perfect reflector, then there would be some probability that light would get absorbed each time it strikes the surface. Since light is traveling so quickly, it wouldn't take long for all the light to get absorbed. Unfortunately there are no such materials to build the container from and, even if there were, you'd have to figure out a way to remove the light source from the container and seal it (so that it was perfectly reflecting on all surfaces) before the light escaped from the opening. That would be quite a challenge indeed. Also, once you opened that theoretical container the light would all escape instantaneously so that the most you might see is a very brief flash. Real materials quickly absorb all the light when a light source is extinguished or blocked.  more