Mass-Energy Equivalence
Contents
Key Stage 4
Meaning
Mass-Energy Equivalence is the observation that energy and mass together form a conserved quantity in a nuclear reaction or decay.
About Mass-Energy Equivalence
- Energy and mass are related by Einstein's famous equation \(E=mc^2\).
- Energy can become mass and mass can become energy.
- Energy becomes mass in a particle accelerator which gives particles so much kinetic energy before they collide that during the collision that energy becomes mass and creates new particles.
- Mass becomes energy in nuclear reactions and nuclear decays.
- When a nuclear reaction takes place the mass of the products is less than the mass of the reactants as some of the mass has been converted into energy and transferred away by gamma-rays.
Key Stage 5
Meaning
Mass-Energy Equivalence states that mass is equivalent to energy and energy is equivalent to mass related by the equation \(E=mc^2\), and that mass-energy is a conserved quantity.
About Mass-Energy Equivalence
- Mass-energy equivalence is observed in the interactions between subatomic particles.
- Protons and neutrons bound in the nucleus have less mass than free protons and free neutrons as energy is released when the nucleons bind together.
- In a particle accelerator, particles are given so much kinetic energy that when the collide with particles travelling the opposite direction much of that energy can become mass causing the production of new particles.
- High energy photons (Gamma-rays) may have enough energy to engage in pair production in which a gamma-ray becomes a particle-antiparticle pair.
Equation
\(E=mc^2\)
Where
\(E =\) The rest energy of a particle.
\(m =\) The rest mass of a particle.
\(c =\) The speed of light (\(3.00\times10^{8}ms^{-1}\) in a vacuum).