[填空题]
1.A beam of electrons is incident on an iron foil (Z=56) ahy jyf87wxxg p6+b0 9- ojsq.nnd3* 0zub b,vc(ivkhc z8qg.:l gp9*gkl electrons are diffracted. In the experiment, electrons have initial kinetic energy of 42 GeV. The first diffraction minilu9gc(v l ghi*:g k.,z8vpk 30bqbz*c mum is observed at an angle of $49^{\circ}C$ from the average position of most of the electrons detected.
(1)Calculate the density of the iron nucleus. $ρ$ = $\times10^{17}\,kgm^{-3}$
(2)Using the diffraction information given, estimate the radius $r$ of the iron nucleus . r = $\times10^{-15}\,m$
2.In another experiment, alpha particles are emitted towards iron foil with an initial kinetic energy of $125\,ke\,V$. Estimate the distance of the closest approach to the iron nucleus of the alpha particles. r = $\times10^{-14}\,m$
