These particles are negatively charged and largely deflected by magnetic and electric field. The speed of it is 50% of the speed of light but it can be increased up to 98%. Its mass is the same as that of electron i.e. 9.11 x 10-31 kg. Its existence can be detected by photographic film and cloud chamber. These particles can produce fluorescence. Their penetrating power is more than that of the Alpha particles.
A high-speed electron or positron, especially one emitted from the nucleus of an atom in radioactive decay. beta particle in Science Expand. beta particle. A high-speed electron or positron, usually emitted by an atomic nucleus undergoing radioactive decay. The motion of these particles can be stopped by a 3mm thick aluminium sheet. Beta particles can produce enough ionization in a gas.