So we did a series of microwave optics experiments in lab. We determined the wavelength of microwaves produced by a transmitter and we measured the interference and diffraction patterns due to various slits (double slit, single slit, circular aperture, etc). Well, for one of the apertures we used just the horn of the receiver....the horn width was the slit. However, for some reason on the "horn as the aperture" run the angle we measured wasn't the correct angle to be used in the diffraction formula. It would be trivial for me to draw a picture and determine the relationship between the angles if I could remember what the apparatus looked like! It has been a few days since I did the experiment and I am not feeling particularly sharp right now....but I need to get this damn report done by tomorrow. Is anyone familiar with the typical microwave diffraction apparatus used?