Through what potential difference (in Volts) must electrons…

Through what potential difference (in Volts) must electrons be accelerated if they are to have the same wavelength as an X-ray of wavelength 0.210nm?   Through what potential difference (in Volts) must electrons be accelerated if they are to have the same energy as an X-ray of wavelength 0.210nm?  

A 4.78 MeV alpha particle from a 226Ra decay makes a head-on…

A 4.78 MeV alpha particle from a 226Ra decay makes a head-on collision with a uranium nucleus.  A uranium nucleus has 92 protons.    What is the distance (in femtometers, i.e. 1e-15m) of closest approach of the alpha particle to the center of the nucleus?  Assume that the uranium nucleus remains at rest and that the distance of closest approach is much greater than the radius of the uranium nucleus.