Glow in the dark thingies

[Kit]

My toddler has a glow in the dark beaker and a night light, both of which are plastic and apparently work by absorbing the light during the day and releasing it at night.
How does this work? And is there an optimum light exposure time to ensure that they carry on glowing throughout the night - I'm fed up of putting her back to bed at 3am when she can't find her drink because her beaker has run down!

[praxis]

Glow in the dark things are a bit of a misnoma! The objects are absorbing light and retaining some of that energy stored but some is also being given off as light again, but because it is daytime you can't see it; you start to see the objects glow becausre the light around is lessening. The objects will then start to get duller as they use all the stored energy - putting the glow things close to a lam may help as these often store light as heat as well but take care as they may get too hot!

[xyzzy@bok]

glowinthedark stuff; isn't it radioactive - like luminous watches?

[anthomson]

The substances that 'glow' are called phosphors ( also use in tv screens for the same reason ). Some Phosphors will 'persist' much longer than others e.g Strontium Aluminate. You can also combine them with radioactive elements (like radium) to get them to glow continuiously. I remember reading that there was a high incidence of tongue cancer in an american city ( detroit I think ) where the workers who painted luminious watch dials used to lick the ends of their piant brushes.

[anthomson]

I assume it will only take a few minutes to 'charge' the beaker, and once fully charged it will always glow for the same period of time. So I guess all you can do is 1: Make sure it is fully charged when your daughter goes to bed i.e. make sure it was exposed to bright light for 10 minutes before bedtime. 2: Recharge it if possible during the night - maybe before you go bed. You could of course try charging it with a radioactive source as mentioned above - but this might have the unwanted side-effect of making your daugther glow in the dark as well.

[Kit]

Actually, anthomson, a glow in the dark child could be very useful - may take up the suggestion!

[Squirrel]

I don't know the answer as such (bear with me) but I can hazard a guess.

When most substances absorb light, a photon of the light collides, so I'm told, with an electron orbiting the atom. All the energy that the photon contained becomes transferred to the electron, causing it to jump to a higher atomic orbit than it was previously at. In any given atom, there are only a limited number of these shells, each shell has a specific energy level, and as such only specific energies of photon (i.e. specific colours of light) can be absorbed. Now comes the bit I'm not so sure about: the electron(s), having been given extra energy, fall back down to a lower shell after a random time (the shell they came from, probably) and a photon, of energy equal to the difference between the energies of the shells, is emitted. I think that most materials will emit light in the infrared range (felt as heat) but that these glow-in-the-dark "thingies" are have just the right shell layout as to emit photons some way into the green range of the spectrum (as well as other frequencies, perhaps invisible). I hope that was the kind of answer you meant; someone might be able polish it up for me.

[Kit]

Whether it's right or wrong, Squirrel, I think you deserve 3 stars for effort! :-)

[Gef]

Just to reassure any casual visitors to this site. Modern luminous devices do not use any radioactive material and are harmless (assuming you don't eat them). The story about the tongue/mouth cancer is true but comes from the 1920s and 30s when the nasty effects of radioactivty had still to be discovered. Marie Curie, joint discoverer of two new radioactive elements in the early 20th century, died from cancer as a result of her pioneering work.

[Hamish]

The 'charging' of the phosphoresance process depends on total absorbd light. The being the case you can rapidly charge things by using a flash from a camera. If you put your hand over a phosphoresant 'exit' sign and set off a flash you will see the sign glowing for a few seconds even with the lights on. turn the lights of and you see a silloett (?) of your hand.

[ilanga]

'Luminous painters' were encouraged by their employers to use the luminous paint as a sexual decoration, make-up, there was even a glow-in-the-dark drink released which was apparently good for impotence and depression! Decades later, these employees sued their employers because of their high rate of cancer. Some had to be carried into court to testify because they were so crippled, any many couldn't even raise their hand to the bible to swear the oath!

[shybearuk]

Further to the earlier answers, see the following link: http://new.theanswerbank.co.uk/Article.go?id=2522&
category_id=8