If the mass of neutron is 1.7x 10-27 kg, then the de-Broglie wavelength of neutron of energy 3 eV is: (h= 6.6x10-34 Js)

mn =  1.7  ×  10−27  kg               E=3eV,      λ=?E=P22m   ⇒   P=2mEλ  =  h2mE  =  6.6 ×  10−342 ×  1.7  ×  10−27  × 3  ×  1.6  ×  10−19                       =  6.6  ×  10−344.04  ×  10−23                       =1.65  ×  10−11  m