Young's double-slit experiment
The base version of this experiment is very simple. It requires only a double slit device like the one in the picture, something to hold the double slit device still, and a good laser such as the kind that is used by workmen to "draw" straight lines when they are building. The laser is supported so it can only be moved on purpose. It is aimed at the central point between the two slits from a point about one half meter away. Something like a movie screen or a smooth white wall is put up on the other side of the double slit device several meters away. When everything is fixed, a pattern of light and dark bands will show up.