There are all sorts of learning objectives you can teach with this one from early primary through to late secondary:
- Light & shadow, color and vision
- Electric circuits - basic series circuits, circuit symbols and diagrams, switches, LEDs and batteries
- Microbes and diseases - transmission of diseases, hand washing and infection, bacteria
- Atomic theory, the atomic model and electron shells, fluorescence and phosphorescence
Step 1: What You'll Need
- A couple of blank PVC ID cards
- A 3mm ultraviolet LED
- Some 5mm (or 1/4") thick foam of some sort that squishes and returns to shape again
- 1 x CR2032 lithium battery
I've put together a few links below of suggested suppliers and parts - with postage costs and minimum quantities you're probably looking at $2-$3 each if you order them in 100+.
If you do the build yourself, this is what you'll need:
- ID Cards: http://www.smartcardsupply.com/Content/Cards/cards.htm - the cheapest blank ones here work out at about 15c each in packs of 100 and you'll need two for each card. These are pretty standard world-wide.
- CR2032 Batteries: http://search.digikey.com/us/en/products/CR2032/P189-ND/31939 - these ones are 28c each
- 3mm UV LEDs: http://search.digikey.com/us/en/products/UV5TZ-395-30/492-1321-ND/2407229 - about $1 each if you get 25 or more. Something from 390nm to 405nm works OK but the lower the wavelength the better.
- Foam: http://mdbuyinggroup.com/products/podiatrist-wholesale/plastazote%C2%AE-14-medium - about $11 which would be enough to make 100. I used 5mm, but 1/4" works as well. There may well be cheaper foams - type is not crucial as long as it is about this thickness - just needs to be able to be squished and return to its original shape.
Step 2: The Foam Insert
Now you'll need to stick the foam onto the card - I used two strips of special high-strength double-sided tape, but for most people a glue gun will be a better choice. It works best just putting adhesive along the two long edges I've found.
Step 3: Put in the Battery
Step 4: Attach the LED
Now push one leg underneath the cell (will go between the card and foam), and the other leg should go above the cell.
If you have done it correct, when you press down on the leg which is on top of the cell, the LED should glow purple.
If it doesn't glow at all, pull it out, rotate it 180 degrees (so the opposite leg is on the bottom), and put it back in.
If it glows all the time (without pushing), you will need to pull it out, spread the legs further apart, and put it back in again.
Step 5: Complete the Other Side
Step 6: Investigating Fluorescence
Children love looking at secret marks with these. Look at foreign bank notes, passports, drivers licenses - even a 2nd class (UK) stamp has a hidden mark on it. Tonic water fluoresces (only slightly), credit cards are great as well and usually have a couple of secret marks on.
Also try looking at the printed marks on (posted) envelopes - they are often printed in a fluorescent ink that helps the sorting machines work out where they are going.
There are countless other fun things to look at - some minerals will fluoresce, some vitamin tablets and even petroleum jelly (vaseline) glows, albeit not very brightly.
With younger children I introduce this by looking at the spectrum and the colors of the rainbow. We then explore the two 'colors' that are just beyond our vision past the red end and violet end respectively; ultraviolet and infrared.
With older (high school) students looking at the atomic model, this is a great opportunity to look at electrons - what we're doing here is actually exciting electrons to a higher quantum state; when they relax to their ground state they then release a photon of light, typically at a longer wavelength, which conveniently for us is now in the visible range so we can see it brightly. The LEDs we are using here are actually on the end of the visible range, hence why we can see the purple light coming off, but we can still consider the light as being ultraviolet. You can read more about fluorescence here.
The type of UV light we are using here is not dangerous at all - it is only the shorter wavelengths that cause sunburn and skin cancer. I consider this project safe enough for any age student as long as they are old enough for the small parts not to present a choking hazard.
Step 7: The Mock X-ray Machine and More About Fluorescence
You can do some further explorations into UV by looking at normal copier paper and white clothing. Copier paper and washing powders both have fluorescent substances added to make them glow slightly and appear 'whiter than white' when there is UV present (as there is outdoors). This knowledge can be used to extend investigations into the comparison of washing powders to see if they are really cleaning the best, or are getting a helping hand by using fluorescence.
Step 8: Microbes & Disease
I usually try to do this with a stronger professional UV torch although it will still work well with these ones in a darkened area.
Your students will be amazed at how badly they wash their hands - areas such as fingernails and backs of hands are often glowing pretty strongly!
You can also make a great demonstration of disease transmission by using the glitterbug products and getting children to shake hands - again, stronger UV lights help particularly after two or three handshakes.
Step 9: Forensics
Scientists also use UV light to look for blood stains and finger prints using other chemicals, although for some fun science investigations you can easily mock up both of these using the glitterbug powder or lotion mentioned in the last step, creating hidden finger prints and blood spatter (perhaps for older students!).
Step 10: Energizing Glow in the Dark Material
This is just plain fun for younger children, but can be used to great effect talking about light and shadows. By placing objects over the sheet and shining the light on them you can create 'semi-permanent shadows.' With older children you can look at Phosphorescence .
Step 11: Microbiology
This is more suitable for high school and university investigations.
Step 12: The Natural World
Step 13: Other Experiments
It's great fun making this into a 'Spying & Invisible Ink" session. User Johenix suggested a great variation (pictured above) which has a white LED on one end and a UV on the other. One side of the card has a table for morse code printed on. This would make a great 'spy card' for kids to make.