# Properties of beta rays

1. $\beta-particles$ has negative charge and its mass is equal to that of an electron.
2. All $\beta-particles$ emitted from a substance have big range of velocities anywhere from 0.3c to 0.9c where c is the speed of light. Note that, at high velocities e/m decreases indicating the increase in mass of the particle according to Einstein’s equation $m=\dfrac{m_o}{\sqrt{1-\dfrac{v^2}{c^2}}}$
3. They have low ionizing power so they cover large range.
4. They can affect photographic plate.
5. They can produce fluorescence in willemite, barium platinocyanide etc.
6. They are deflected by magnetic and electric field. Their direction of deflection has proven that they are negatively charged particles.
7. $\beta-particles$ can penetrate through thin metal foils and their penetration power is higher that that of $\alpha-particles$
8. The value of e/m for beta rays was proved to be the same as that of cathode rays. The charge on a $\beta-particles$ was observed to be the same as the charge of an electron. Therefore $\beta-particles$ are identical with electrons.