DIY Photoelectric Effect and Electroscope

I suppose I could claim this is seasonal – it does use tinsel, after all! But in reality it’s just that I’ve gotten around to producing the resource to go along with this post.

 

 
While teaching AS Physics (AQA A, if you care) I requested, as usual, the apparatus to demonstrate the photoelectric effect; this is one of the first experiments that demonstrated particle properties of light, as later explained by Einstein. The gold-leaf electroscope arrived, with a piece of zinc and a UV lamp. It didn’t work. I did what all good physics teachers do; after messing around a little with the equipment then swore where the kids couldn’t hear me. When I had the chance, I had a look online.
 
This is a notoriously unreliable experiment in the school science lab. I hoped for some hints and tips to make it work better. What I found was far superior – a version my students could build for themselves in a lesson from odds and ends, starting with a drinks can. It was demonstrated on Youtube and I followed links to a set of instructions, but thought they were rather complicated for the average student. So here’s my own version; drinks can electroscope as a pdf.
I must emphasize that this is not my idea, but I have produced a student-friendly version of the instructions. As far as I can tell this grew out of a demonstration at the American Physics Teachers Conference, and of course there are other home-made electroscopes around.
 
According to the original instructions, a ‘hand sanitizer’ works well as the UV source. You can get these in the UK direct from the supplier, Wallace Cameron, for about £15.
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2 thoughts on “DIY Photoelectric Effect and Electroscope”

  1. It all sounds very simple and easy but I have failed to make the tinsell to stay charged despite every effort to keep the electroscope insulated insulated,tried different types of objects to charge it, different cans. Nothing worked. Good idea if one can make it stay charged!

    1. I found it worked pretty well; sliding the charged rod through, rather than stroking it along the tinsel, gave the best result. have you tried the usual hairdryer trick to make sure the air is dry enough nearby?

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