What level of radiation can travel through paper?

Alpha radiation consists of helium nuclei, which are relatively heavy and carry a positive charge. Because of their larger mass and charge, alpha particles have a very limited ability to penetrate materials. They can be stopped by something as thin as a sheet of paper or even the outer layer of human skin.

In contrast, beta particles, which are high-energy, high-speed electrons or positrons, have greater penetration abilities and can pass through paper but are typically stopped by plastic or a few millimeters of aluminum. Gamma radiation, being a form of electromagnetic radiation, has much higher energy and can penetrate much more substantial materials, including paper, but also lead and thick concrete.

Therefore, while alpha radiation cannot penetrate paper, it is crucial to recognize that beta and gamma radiation can indeed pass through it. The properties of alpha radiation make it the correct answer regarding what level of radiation is effectively stopped by paper.