The energies of beta particles from radio-active elements are determined by measuring the radii of curvature of their paths in a magnetic field of know flux density B. The circular path traversed by the beta particles of velocity v is governed by the relation Bev = (mv

^{2}/r). Therefore v = B r (e/m).From the geometry of the arrangement, the radius of the circular path r can be found. The value of e/m can be assumed. Hence, the velocity v can be calculated.

For particles moving with very high velocities, the kinetic energy of the particle,

## Continuous beta-ray spectrum

With the beta decay the freely becoming Energy becomes on the emitted particles Electrons and Neutrino after a Wahrscheinlichkeitsgesetz (it means probability law) distributes, so that the beta-ray spectrum continuous spectrum is. It extends decreased by the energy zero up to the upper border, those by the transformation energy by those Recoil energy the daughter core is given.

Maximum beta energies:

- Neutron 0,78 MeV (β
^{-}) ^{11}C 0.96 MeV (β^{+})^{37}K 5.1 MeV (β^{+})^{20}F 5.4 MeV (β^{-})

## Discrete beta-ray spectrum

If during a beta decay the output core changes into different energy conditions of the subsequent core, then several simple beta-ray spectra overlay to a complex beta-ray spectrum. Those lively Daughter cores go through sending of Gamma radiation into that Initial state over or they enter their energy on Orbital electron off, that that K, L or a higher bowl belongs. In this way a discrete beta-ray spectrum develops. This procedure is called conversion.

Another interpretation of discrete beta-ray spectra lies in the fact that those Gamma radiation, which develops during the transition of the lively daughter core to the initial state and which electron sheath of the atom penetrates, one Photoelectric effect releases, by Electron the covering takes up the energy of the gamma quantum and with an energy equal the gamma energy decreased by those Replacement work the electron the atom leaves. In many cases the continuous and the discrete beta-ray spectrum overlap themselves.