deflection of alpha particals decreased by changing the K.E.of alpha particals?

Question

deflection caused by aluminium foil are less than that by gold foil in alpha particals,why?

Answer 1

Aluminum has about 27 nucleons while gold has about 197 The diameter of the gold nucleus is therefore about 1.8786 times that of the aluminum nucleus, with a cross section about 11.087 times that of aluminum. Alpha particles therefore encounter gold nuclei about ten times as much as they encounter aluminum nuclei in the same thickness of foil.