How do beta particles behave in a magnetic field?

Beta particles, which are high-energy, high-speed electrons or positrons emitted during radioactive decay, exhibit behavior in a magnetic field due to their charge. When a charged particle moves through a magnetic field, it experiences a force that is perpendicular to both its velocity and the direction of the magnetic field. This phenomenon is explained by the Lorentz force law.

As beta particles are charged, they are not merely attracted or repelled by a magnetic field; instead, they experience a deflection in their trajectory. The direction and magnitude of this deflection depend on the strength of the magnetic field and the velocity of the beta particles. The resulting path will typically be circular or helical, depending on whether the magnetic field is uniform and the motion of the particles.

Therefore, the behavior of beta particles in a magnetic field is characterized by their deflection due to the exertion of the magnetic force acting on the charged particles. This is why the answer indicating that beta particles are deflected is the correct choice.