1. The problem statement, all variables and given/known data A beam of electrons strikes a barrier with two narrow but equal-width slits. A screen is located beyond the barrier, and electrons are detected as they strike the screen. The 'center' of the screen is the point equidistant from the slits. When either slit alone is open, 10 electrons arrive per second in a very small region at the center of the screen. When both slits are open, how many electrons will arrive per second in the same region at the center of the screen? (Question 11, Chapter 4) 2. Relevant equations Not really sure... This is why I'm stuck. I can't think of any equations to use to approach this type of problem. 3. The attempt at a solution My intuitive guess is 20.. For obvious reasons. I just don't see my teacher putting such an informal and simple question on our assignment. Is there a more formal way to solve for the answer to this question?