So given a deBroglie wavelength 1.8nm and the equations E=hf and E=1/2mv^2
you can get v = 2h/m*(1.8*10^-9)
but this is 2 times the expected value. Wherever I look online people use the momentum p instead to calculate the speed v. But I don't understand why the working above using those two equations gives you an incorrect answer. Obviously I must be missing something here, I was thinking that perhaps more of the energy is stored in the neutron and isn't actually stored as kinetic energy.
Any help is appreciated.
