Standing waves on a spring

Posted: October 29, 2014 in Institute of Physics
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You might have seen/done this one before, but the teachers I was showing it to found it quite useful, so I thought I would post it on talkphysics. The nodes and anti-nodes are a lot clearer when the amplitude of the oscialltions is higher, but I was told the signal generator broke the previous vibrator when set too high, so I was a bit cautious with this one.

There are several teaching and learning points with this demo. For example, you could get the students to calculate the speed of the wave along the spring, as we know the frequency from the signal generator and can measure the wavelength (for example by measuring the length of the stretched spring with a ruler).

Once we know the speed of the wave, we could ask the students to predict the next frequency in which a standing wave will form.

What else would you use this demonstration for? What other questions would/could you ask?

Flipping arrow – awesome refraction demonstration

Posted: April 26, 2014 in Institute of Physics, Thoughts and ideas
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When @CardiffScience posted (on Google+) a video demonstration of an arrow drawn on a piece of paper that flipped direction when seen through a glass of water I knew I had to try it myself and write this post. The video below shows the demonstration which is pretty neat, but carry on readying below the video for what I think is the explanation.

As some of you might know, I am one of the Editors of Talkphysics.org with David Cotton and he posted the below photo on this thread, which is think is a convincing explanation of what goes on in my video of the flipping arrow. If you trace the path of the three rays in the Dave’s photo you can see the ray that start from the top slit from the ray box ends up at the bottom on the multimeter. This is essentially what is happening in the video, so the light reflected by the right side of the arrow gets refracted by the water inside the glass and ends up on the left when it reaches the camera. Looking at the photo above though gave me an idea, i.e. “If I go close enough to the glass I should go beyond the focal point of the glass lens and see the arrow flipping again!” – WRONG! That didn’t actually happen. However, I just noticed that Dave’s liquid was Glycerine (at least if the name of his image file tells the truth), so I wondered whether the refractive index of glycerol was such to cause less bending inside the glass, but I was wrong again. In fact, water has a refractive index of 1.33 and glycerol of about 1.47, so there should be more bending of light inside the glass. I still haven’t figured out why I can’t flip the image again if I go close enough to the glass, but I still think it was worth posting this article and if you know the answer, please leave a comment! Thanks!

Last night we had our first TeachMeet entirely dedicated to the teaching of Physics in Gloucestershire and despite the inclement weather and illnesses a few teachers from the region managed to come and give some great presentations! A particular thank you goes to Helen Rogerson (@hrogerson) who took the time to record two videos for us to watch. And that’s what we did! In fact, the TeachMeet began with Helen’s 7 minutes video which showed some great stuff she does wit their learners and parents with revision. Of particular interest to the participants was the part on Electromagnetic Induction, which sparked a series of interesting discussions and caused us to go back and watch the lovely demonstrations several times. This was indeed a lovely part of our TeachMeet that I believe stood out from others I have attended and organised in the past. In fact, it is quite easy to rush through all the presentations trying to fit everyone in and forget about allowing the participants time for discussion and to network. But last night ideas on alternative ways to use the equipment and extensions to the demos were freely flowing and created a very relaxed atmosphere from the very beginning.

Next, IoP award winner Kevin Betts showed a great demo of “Dancing Waves” on custard on the cone of a speaker. You can see his Magic in the video below.

Steve Rice was up next showing us how he uses  a sparkler attached to a drill to simulate the gravitational attraction between the earth and the moon. As the sparkler spins around the drill, the sparks fly along the tangent to the circle drawn by the sparkling tip, which helps the learners visualise what would happen if the gravitational pull between the two heavenly bodies suddenly disappeared. I liked this demonstration because it allows the learners to think outside the box and stretch their understanding in the realm of the abstract.

Below is a video of these two lovely demonstrations.

After that it was my turn to talk about how I used one of the best iPhone/iPad apps I have ever come across, the Vernier Video Physics, with my learners. You can find this resources on the TES website here. It was also the first time I publicly announced my new role as Science Lead at TES commencing in January and I explained that, although I occasionally use it already, I will actively interact with the Twitter sphere using @TESScience from then.

We closed the TeachMeet with our sponsors’ raffle, which included a very generous box full of Nelson Thornes books, ranging from GCSE revision guides to a Muncaster tome 4th edition. ThinkBuzan also offered a free copy of their Mind Mapping software iMindMap 5 Ultimate (the last two links are affiliate links, so Google iMindMap 5 instead, if you are bothered by this sort of thing).

Two other teachers emailed me apologising they couldn’t attend due to illness, but they sent links to interesting stuff that they would have shared in person, if they had been there. The first is the YouTube video below about mixing colours with glow sticks shared by Bernadette Willey.

The other tool is Poll Everywhere shared by Lewis Matheson, which seems a really neat tool to use with mobile devices!

I thoroughly enjoyed myself last night and I learnt a lot (as usual) from innovative colleagues in the Gloucestershire Network. I hope to see many more at our next events in the new year.

I found the iSeismo App for iPhone a few months ago thanks to an email on the PTNC (the Institute of Physics mailing list). It is a free App and also a brilliant one. I am developing resources for the WJEC Separate Science Specification (Physics 3) here at NGfL Cymru (National Grid for Learning Wales) and one of the topics is Seismic Waves, so I couldn’t resist the temptation to create an activity that would take advantage of such a great App!

iSeismo displays a seismograph for movements along the x, y and z axes using the inbuilt accelerometer in the iPhone and it is very realistic and quite accurate too. The needles look just like a real Seismographer writing on paper rolls, but with this electronic seismographer you can freeze the screen and pause it at a particular moment, as well as other interesting things.

I am giving you another sneak peek of what’s coming soon on the NGfL Cymru website. Below is the video that I created this morning to go with this activity in Wallwisher. The cool thing is that when the iPhone was at rest I received an email and the phone vibrated. The needles on iSeismo showed a vibration along the x and z axis, but not on the y-axis. So, the vibrator must be fixed onto a plane which is perpendicular to the y-axis. I bet you didn’t know that about the iPhone, did you? At least about the iPhone 3GS.

I created the Wallwisher wall as an example for teachers, but to use it with your classes you would need to register with Wallwisher and create your own wall by linking the video to the YouTube video in this blog.