The type of radiation that barely passes through a piece of paper is alpha radiation.

Here's why:

* Alpha particles are relatively large and heavy, consisting of two protons and two neutrons. This makes them slow-moving and easily stopped by even a thin barrier like paper.

* Beta radiation consists of electrons or positrons, which are much smaller and faster than alpha particles. They can penetrate paper, but can be stopped by a thin sheet of metal.

* Gamma radiation is a form of electromagnetic radiation, like light but with much higher energy. It is much more penetrating than alpha or beta radiation and can pass through several centimeters of lead.

So, while alpha radiation can be dangerous if it enters the body, it's easily stopped by common materials like paper, making it less hazardous from an external source.