Here a scope, there a cope, everywhere a spinthariscope

The spinthariscope — see atoms decay before your eyes!

A small radioactive source (the details of which we will discuss later) emits alpha particles that collide with a zinc sulfide (ZnS) screen. This screen gives off flashes of light (called scintillations) at the places the alpha particles hit. These minute flashes are magnified by a simple lens and can be viewed through the eyepiece. Every flash the viewer sees is the trace of a single atomic nuclear decay. By adjusting the bottom screw, one can effectively increase or decrease the rate at which alpha particles hit the screen, transforming a flood of particles into a trickle, or vice versa.

This is a pretty neat effect, and is worth blogging about in itself, but the spinthariscope also has historical significance: it was the first device invented that is able to detect individual radioactive particles, a precursor to the Geiger counter!

I got one, too, though mine lacks the adjustment screw. Neat flashes of light, though, as long as I am not wearing my glasses — I need to get my eye right up to the eyepiece. Unfortunately the flashes have proven too dim to capture on a camera. The low-light viewer we have in the lab didn’t help; it’s geared more to being sensitive in the IR (and shifting it to green, which helps the eye more than the camera) than to amplifying raw signals.