Light Party does Science! (Part 5) The Science!

We can have a lot of fun with all types of glow-in-the-dark sciency stuff, while thinking about how God is the source of all light and we can shine his light out.

Here are lots of ideas for a light party with a science twist, such as luminous letters, fluorescent food, and glow stick (naturally) games.

How to get the best effects

Close all the curtains in your room and swap the normal light bulbs for UV (black light) bulbs (click) *, or put the UV bulbs in desk lamps to see the cool fluorescent effects. If you cannot blackout the room, use large tents or gazebos for your UV dens.

Luminous objects will glow in the dark after then have been ‘charged up’ with normal or UV light. Fluorescent things need UV light to glow. Reflective things only look bright when you shine light directly on them. Many safety objects are fluorescent, luminous and reflective.

A note for buying supplies: Not everyone in the advertising industry knows what ‘fluorescent’ means. Some people think it just means brightly coloured. ‘Neon’ or ‘Day-Glo’ on packaging might mean fluorescent or glow-in-the-dark or it might just mean bright. If in doubt, take a small UV pocket torch when shopping.


The Science Bit

What is UV?

There is a whole lot more to light than just the rainbow of colours we can see. Before red in the rainbow is an invisible colour called infra-red, and at the other end, just beyond the purple, there is ultra-violet, or UV. This is sometimes called ‘black light’ because we cannot see UV. Reindeer, and butterflies and bees can all see UV light.


Is UV safe?

Our skin reacts to strong UV light by turning darker, and can be damaged by too much UV, so we wear sunscreen in the summer. The UV from torches is very much weaker, so you won’t get a tan and you don’t need to wear sunscreen. But obviously, don’t go staring into torches.

What does ‘fluorescent’ mean?

Fluorescent things absorb the invisible ultra-violet (UV) light and send it back out as visible light. Sunlight and some artificial lights contain UV as well as visible light, so fluorescent objects may appear brighter that we expect because of the extra light given out. Sometimes they are call ‘Day-Glo’ or ‘neon’.

Many washing powders contain UV dyes so that your clothes appear brighter and whiter. This is why many white clothes fluoresce under UV light. Highlighter pens have fluorescent ink and many plastic cards have hidden security that you can only see in UV light. Check out your money or driving license – it’s really cool!

fluoriteHow does it work, is it the same as luminous, and why is fluorescent spelled funny?

Stand Back – here come the science!
We can think of atoms as being like the solar system, with electrons that circle round like planets round the sun. Some atoms have electrons that can absorb UV light. When they do this, the electrons get excited, and jump out to a higher orbit with the extra energy.

After a while they get bored and jump back to their original orbit, giving back the energy they absorbed. But they give it back in a slightly different form: as visible light instead of UV light. This is called fluorescing and was first noticed in a type of stone called fluorite, and was named after it.

A similar thing happens in glow-in-the-dark substances, such as the luminous paint that is used to make alarm clock numbers or star stickers visible at night. In this case the paint contains atoms which absorb normal visible light and send it back out, slowly for several hours. Luminous paint often gives out pale green light.

Glow sticks work differently. They have two chemical which mix when you ’snap’ the sticks. The chemical reaction gives out energy in the form of light. This is how fire flies and glow worms work, too.

Other items are called ‘reflective’. These include road signs, hi-vis clothing and the white paint on roads. One way this works is with tiny glass beads that gather all the light shining on them and reflect it back the way it came instead of scattering it everywhere. So a hi-vis jacket will catch a car’s headlights and shine the light back to the driver to make walkers and cyclists more visible at night. Cat’s eyes work the same way, which is why they sometimes shine very brightly.

All these things give out light, but they have to get that energy from somewhere: usually from light that shines on them. We can use the science of fluorescence to think about how we can shine out light because we live in God’s light.


Light Party does Science!


* Clickable links

The clickable links will take you to suggested items on Amazon via an affiliate link. If you purchase any items after following an affiliate Amazon will make a small donation to support this ministry. So feel free to splash out on that diamond-studded Porsche. No personal data is passed in either direction, and the price you pay is exactly the same.

Please note: The suggested items are necessarily exactly the same as the ones I use. So while I have linked to ones that are as close as possible to the ones tested so I cannot vouch for their suitability.

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