Is an empty room really empty?

Predict, before you switch on

Three questions. No right answers yet.

Question 1. You switch the detector on in a normal classroom with nothing in front of it. What will you see in one minute?

Lock in my answer

Prediction locked. You will find out at the bench.

Question 2. Three particles hit the sensor: an alpha, a beta, and a cosmic muon. Which one leaves the biggest, densest mark on the grid?

Lock in my answer

Prediction locked. You will find out at the bench.

Question 3. In one minute indoors with no source nearby, how many straight muon tracks will you catch?

Lock in my answer

Prediction locked. You will find out at the bench.

Observe

What did the detector record?

Run the detector with nothing in front of it. Count what you saw and fill in the table.

Track shape	Particle type	How many?
Single dot	Photon (X-ray or gamma)
Curly or worm-like	Electron (beta)
Round blob	Alpha
Straight line	Muon

Explain

What does it mean?

Was the "empty" detector really empty? Which of your three predictions were right, and which surprised you? What does that tell you about radiation in the room?