I've read in books that one can't put one's hand through a table because the table offers a "Normal Reaction" to the hand. And it is also stated that this force is electromagnetic in nature. But what is this force? Can it be explained using classical electromagnetism "in terms of something I'm more familiar with"?
Moreover, if it is this force that stops my hand from going through the table, why is it that certain other solid substances, like sand, don't produce the same result?
Also, is there any limit to this Normal reaction? I mean on pushing too hard my hand might go through the table. Is there any upper limit to this force?