Phosphorescence silhouette “photos” can be taken with a camera flash due to persistence of the image.
“Continue reading” for more examples of phosphorescence and links…
The sheet is a square yard of “Kryptonite” from Scitoys. It is made of Strontium Magnesium Aluminate, doped with Europium and Dysprosium. It can be charged with an hour of sunlight and give 12h of phosphorescence.
Fluorescence is the immediate emission of light less than 10 ns after the initiating exposure.
i.e. Glows while lit (most dramatically with UV)
Phosphorescence (Wikipedia) is the delayed emission of light more than 10 ns after the initiating exposure.
i.e. Glows in the dark after being lit.
Radioluminescence Glows constantly due to radioactivity.
Red phosphorescence after shining a green laser on Strontium Aluminate : Europium 2%. (Sr Al2O3 : Eu). This fades over seconds with a faint glow being present after minutes.
I was doing some experiment with liquid nitrogen (LN2) hence the gloves, but I have no recollection about it.
This is a 1930’s watch face with radium and phosphor added to the numbers to give a permanent glow. It no longer glows due to damage to the phosphor. It is not loss of radioactivity from the Radium-226 which has a half life of 1600 years. Flash a bright light on it and the numbers will glow very faintly with dark adapted eyes and fades over minutes. This is phosphorescence.
Above is the radium watch face behind an alpha detector film. The right photo is an 8 minute exposure clearly showing the numbers behind the film. Great! But was it the radium doing that?
Could this have been phosphorescence? This is persistent glowing of a phosphor after light exposure. To test this, I kept it in the dark for an hour to remove residual phosphorescence. I then ran a swipe of a violet laser across the 8 and 4 numerals. This will stimulate those numerals only to phosphorecsce.
After a 10 minute exposure of the radium containing watch face behind an alpha viewing film, the only numerals that were lit were those exposed to the laser earlier. All other phosphorescence was long gone and there was no activity elsewhere.
So this concludes that any faint glow from the watch face numerals is due to phosphorescence and not radioluminescence as it was originally made. Ohh well.
Here is the same radium dial phosphorescence from a Wikipedia photo. A radium containing watch face is shown to light up after “previous” UV-A light exposure.
Related pages
Phoshorescent sheetTry something else
Can Crusher for the UniExternal links
Photo Date: Oct 29, 2007