Here are two exercises: 1. ) The proton radius is 0.8fm. What energy electron beam do you need for this resolution, if the target is liquid H2? 2.) A pion radius is 0,65fm. What energy pion beam do you need for this resolution by scattering on the electrons of a stationary target(pi-e scattering)? Why is the beam energy so different than in the previous exercise? ------ Now, i guess the main point in both cases is that the dr Broglie wavelength of the bombarding particle is the best resolution one can achieve. But, if I just go with de Broglie wavelength = spatial resolution , then I get approx. 1,5GeV and 1,9GeV respectively, which is not that different, so I don't understand the necessity of the last question. Also, I don't think the target material is important. Can someone clarify this?