Some of you may remember Dr. Mason at BYU, and some of you may have had him for a class or two (I had him for three classes...). There was one problem in particular that I remember solving in his quantum mechanics class. It went something like this:
Q: Figure out how slow a 75 kg pig needs to be going in order for it to diffract by a minimum of 1 meter through a door way 1 meter wide into a 10 meter wide room.
I will now solve this problem and demonstrate why pigs do not diffract through doorways.
First we have to find the de Broglie wavelength (Note: de Broglie is pronounced "duh Broy" not "Dee Brog-lee-ay" as I learned from a certain Belgian professor). Knowing the width of the slit (the door) and the distance the pig travels (10 m) before it is observed (hits the opposite wall), we can solve for the wavelength of the pig as it diffracts into the room. First we use simple trigonometry to find the angle of diffraction: