Req 5a — Time, Distance, and Shielding

This requirement puts ALARA into action. Instead of talking about safety in theory, you measure how the setup changes the reading. That makes the three main protection tools feel real.

What counts per minute tells you

A survey meter detects radiation events and reports a reading such as counts per minute (CPM). A higher CPM usually means the detector is receiving more radiation events. If the source moves closer, the reading often rises. If it moves farther away, the reading often falls.

The reason distance matters is simple: radiation spreads out. When the detector is farther away, less of that radiation reaches it.

What shielding shows

Different materials reduce radiation differently because alpha, beta, and gamma radiation do not all interact with matter the same way. A light barrier may stop alpha radiation. Denser or thicker material may be needed for beta or gamma radiation.

When you compare three shielding materials, do not just list the readings. Explain why the differences happened. Was the material denser? Thicker? Better suited to that type of radiation?

If you want to explore a radiation issue that shows up in ordinary buildings, the radon option is next.