In a darkened room, use a strong hand lens to look closely at a radioactive (quartz?) watch dial -- you will see tiny flashes of light. (This writer does not believe that quartz is radioactive, but the quartz hands on my clock do glow in the dark.) Now place the watch under a low-power microscope, and observe the dial again.

The radioactive atoms (radium) on the watch break apart and each flash represents a collision between an atomic particle and the coating material on the watch. (This writer does not know if the quartz on watch dials works the same or not.)

You might be interested in researching the work of Marie Curie (1867-1934), a French chemist who studied radioactive elements such as radium and strontium.

It may also be of interest to know that not very many years ago, the hands (and sometimes the numerals) on watches were painted with radium so that they would be visible in the
dark. Then, it was observed that many of the employees at the plants where these watches were manufactured were getting lip cancer, and other cancers in and around their mouths. It seems they used tiny sable paint-brushes to apply the radium to the watches. They would paint on some radium, run the brush between their lips to make the brush come to a fine point, dip it in radium again, and paint some more. This probably had something to do with causing the medical community to become aware that radioactive substances can be dangerous. Further, Mme. Curie had died of cancer. There are just some things we have to learn the hard way.