NUCLEAR PHYSICS
Energy & Mass Equivalence
Einstein showed in his theory of relativity that matter can be considered a form of energy and hence,
he proposed:
• Mass can be converted into energy
• Energy can be converted into mass
This is known as mass-energy equivalence, and can be summarised by the equation:
𝑬 = 𝒎𝒄𝟐
Where:
E = energy (J)
m = mass (kg)
c = the speed of light (m s-1)
Some examples of mass-energy equivalence are:
1. The fusion of hydrogen into helium in the centre of the sun
2. The fission of uranium in nuclear power plants
3. Nuclear weapons
4. High-energy particle collisions in particle accelerators
Nuclear Equations
Page 1 of 12
, Example:
Mass Defect & Binding Energy
Experiments into nuclear structure have found that the total mass of a nucleus is less than the sum of
the masses of its constituent nucleons. This difference in mass is known as the mass defect.
Mass defect is defined as the difference between an atom’s mass and the sum of the masses of its
protons and neutrons. The mass defect Δm of a nucleus can be calculated using:
∆𝒎 = 𝒁𝒎𝒑 + (𝑨 − 𝒁)𝒎𝒏 − 𝒎𝒕𝒐𝒕𝒂𝒍
Where:
Z = proton number
A = nucleon number
mp = mass of a proton (kg)
mn = mass of a neutron (kg)
mtotal = measured mass of the nucleus (kg)
The mas of nucleus is less than the total mass of its component protons and neutrons
Page 2 of 12
Energy & Mass Equivalence
Einstein showed in his theory of relativity that matter can be considered a form of energy and hence,
he proposed:
• Mass can be converted into energy
• Energy can be converted into mass
This is known as mass-energy equivalence, and can be summarised by the equation:
𝑬 = 𝒎𝒄𝟐
Where:
E = energy (J)
m = mass (kg)
c = the speed of light (m s-1)
Some examples of mass-energy equivalence are:
1. The fusion of hydrogen into helium in the centre of the sun
2. The fission of uranium in nuclear power plants
3. Nuclear weapons
4. High-energy particle collisions in particle accelerators
Nuclear Equations
Page 1 of 12
, Example:
Mass Defect & Binding Energy
Experiments into nuclear structure have found that the total mass of a nucleus is less than the sum of
the masses of its constituent nucleons. This difference in mass is known as the mass defect.
Mass defect is defined as the difference between an atom’s mass and the sum of the masses of its
protons and neutrons. The mass defect Δm of a nucleus can be calculated using:
∆𝒎 = 𝒁𝒎𝒑 + (𝑨 − 𝒁)𝒎𝒏 − 𝒎𝒕𝒐𝒕𝒂𝒍
Where:
Z = proton number
A = nucleon number
mp = mass of a proton (kg)
mn = mass of a neutron (kg)
mtotal = measured mass of the nucleus (kg)
The mas of nucleus is less than the total mass of its component protons and neutrons
Page 2 of 12
