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Atomic Mass Unit

In nuclear physics, a convenient unit of mass is the unified atomic mass unit abbreviated as u.
  • The amu is defined as 106339.png mass of a 6C1 atom.
  • 1 amu (or 1 u) = 1.6605402 × 10–27 kg
Masses of electron, proton, and neutron
 
Mass of electron (me) = 9.1 × 10–31 kg = 0.0005486 amu
 
Mass of proton (mp) = 1.6726 × 10–27 kg = 1.007276 amu
 
Mass of neutron (mn) = 1.6750 × 10–27 kg = 1.00865 amu
 
Mass of hydrogen atom (me + mp) = 1.6729 × 10–27 kg = 1.0078 amu
  • The energy associated with a nuclear process is usually large, of the order of MeV.
  • According to Einstein, mass and energy are inter convertible. The Einstein’s mass energy relationship is given by E = mc2.
  • If m = 1 amu, c = 3 × 108 m/s, then E = 931 MeV, i.e., 1 amu is equivalent to 931 MeV or 1 amu (or 1 u) = 931 MeV.
     
    (1 u) c2 = 931 MeV
     
    ⇒ 106358.png or 106368.png




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