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Glossary
221 electromagnetic force : The force that arises between particles with electric charge, the second strongest of the four fundamental forces (page 31). electron : A particle with a negative electric charge that orbits the nucleus of an atom. electron-volt (eV): It is a unit of energy of electromagnetic force with which the elementary particles are held together in an atom. (It is energy acquired by any particle with one unit of charge falling through a potential difference of l volt.)
The force that binds the electrons to the atomic nuclei is about 10 eV., whereas the force which holds protons and neutrons together in neuclei is abcut 10 million eV.
1 GeV=1 giga electron-volt.
giga-100 million. electroweak unification energy : The energy (around 100 GeV) above which the distinction between the electromagnetic force and the weak force disappears (page 32). elementary particle : A subatomic particle that, it is believed, cannot be subdivided. event : An event is something that happens at a particular point in sapce and at a particular time, i.e., it is a point in space-time continuum, specified by its time and place. exclusion principle : Two identical spin-1/2 particles cannot have (within the limits set by the uncertainty principle) both the same position and the same velocity (page 64). field : Something that extends in space and time, as opposed to a particle that exists at only one point at a time. frequency : For a wave, the number of complete cycles per second gamma ray : Electromagnetic waves of very short wavelength, produced in radioactive decay or by collisions of elementary particles. grand unification energy : The energy above which, it is believed, the electromagnetic force, weak force and strong force become indistinguishable from each other (page 46).
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