3.2.1.4
Exchange particles carry the fundamental forces
Particles, Antiparticles & Photons — AQA A-Level Physics
- Forces between particles are transmitted by exchange (virtual) particles, also called gauge bosons.
- A virtual particle exists only briefly while carrying force between two interacting particles.
- There is no instantaneous action at a distance — forces are mediated by these exchanges.
Exchange particles for each interaction
- Strong nuclear: pion ($\pi^{+}$, $\pi^{-}$, $\pi^{0}$) between nucleons; gluon between quarks.
- Weak nuclear: $W^{+}$, $W^{-}$, and $Z^{0}$ bosons.
- Electromagnetic: virtual photonA quantum (discrete packet) of electromagnetic radiation. Its energy is proportional to its frequency. ($\gamma$).
- Gravity: graviton (theorised, not yet discovered).
- The virtual photonA quantum (discrete packet) of electromagnetic radiation. Its energy is proportional to its frequency. has no mass and no chargeA property of matter that causes it to experience a force in an electromagnetic field. Measured in coulombs (C).. It is its own antiparticle.
- Electromagnetic interactions occur whenever two charged particles interact — for example, two electrons repelling each other exchange a virtual photonA quantum (discrete packet) of electromagnetic radiation. Its energy is proportional to its frequency..
Examiner Tips and Tricks
- You must know which exchange particle mediates which interaction.
- This is tested directly when you are asked to draw or interpret Feynman diagrams.