✔ 最佳答案
The use of the equation: KE loss = PE gain is just a result of the Law of Conservation of Energy when applied to electrostatics.
1.No, this is not true. The energy of alpha particles from a given radionuclides is well known. Alpha particles display a "line sprectrum" instead of a "broad spectrum" as in the case of beta particles. All alpha particles coming from a specific radioanuclide have the same energy.
Examples, Americium-241, alpha particle energy = 5.485 MeV; Polonium-201, alpha particle energy = 5.304 MeV
2. The charge on the nuclide has already been taken care of in the equation by the "atomic number Z". The equation applies to alpha paticles approaching the nucleus along a "head-on" collision path. The value of r thus gives the nearest distance from the centre of the nucleus that an alpha particle could reach. Hence, it is the "upper limit" of the size of the nucleus.