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Feynman Diagrams

Feynman Diagrams are graphical representations of the interactions of elementary particles. They are a method of visualising and calculating the effects of electromagnetic interactions among particles and are used to depict all types of particle interactions.Every line connects to one vertex. The direction pointed to by the arrows denotes time, and moving across represents space. This means that incoming particles are represented by lines going in to the vertices and outgoing particles are represented by lines coming out of the vertices.The exchange particle such as the virtual photon is depicted as a wave connecting the two incoming particles and each end of the wave forms a vertex to which the incoming and outgoing particles are connected.

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Specification: AQA Physics (7407), AS-level, 3.2.1.4 Particle interactions. Topic: Particles and Radiation.

Key terms in this lesson

Strong nuclear force
The short-range attractive force between nucleons that overcomes the electrostatic repulsion between protons and holds the nucleus together, becoming repulsive at very short separations.
Lepton
A fundamental particle that does not interact through the strong interaction, for example the electron, the muon and their associated neutrinos.
Baryon
A hadron made of three quarks, for example the proton and the neutron.
Strangeness
A quantum property, given the value -1 for strange particles, that is conserved in the strong interaction but can change by 0, +1 or -1 in the weak interaction.
Momentum
The product of an object's mass and its velocity; a vector quantity, conserved in any interaction provided no external resultant force acts.

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