What are photomultiplier tubes?

A photomultiplier tube is like a super-sensitive microphone for light.

Imagine you're at a tiny concert, just one person whispering in a quiet room. That’s how little light can be. A photomultiplier tube listens to that whisper and turns it into a loud, clear sound so we can hear it, or measure it.

Think of the photomultiplier tube as having layers of helpers. When a single particle of light (called a photon) hits the first layer, it knocks out an electron, like how a domino might fall when you nudge it just right. That one electron then runs into the next helper, which makes more electrons jump up. This chain reaction keeps going, and before long, you have thousands of electrons zooming out, making the tiny light signal much bigger.

These tubes are used in places where even a little bit of light matters, like in night vision goggles, cameras that work in the dark, or even in space to catch signals from faraway stars. They're like detective lights, helping us see things we wouldn’t be able to notice otherwise.