What stops beta radiation effectively?

Beta radiation, which consists of high-energy, high-speed electrons (or positrons) emitted by certain types of radioactive decay, has a specific penetration ability into materials. An aluminum plate is an effective barrier against beta radiation because it has sufficient thickness to absorb and stop the electrons. The electrons are relatively lightweight and are affected by interactions with the atomic structure of the aluminum, leading to their eventual absorption.

When beta particles encounter aluminum, they can collide with the atoms in the metal, losing energy and ultimately coming to a stop. The material needs to be dense enough to effectively absorb these particles, and aluminum strikes a good balance between being readily available, lightweight, and sufficiently dense to stop most beta radiation satisfactorily.

In contrast, options like paper may only stop low-energy beta particles, but not all; glass can stop some beta particles, but not effectively compared to aluminum; and concrete, while providing effective shielding for higher radiation types, is typically over-engineered for beta radiation specifically and is less efficient than aluminum for this purpose. Thus, an aluminum plate is the best choice for effectively stopping beta radiation.