Newton’s Rings

I’ve been trying to show my AH pupils all of the experimental work for Unit 3 during this week, as it’s the last week of the course before their NAB next week.

Having gone over much of the theory before Easter and encouraging them to cover the theory on Scholar, I set up a few of the interference experiments – Young’s Slits with microwaves and using a He-Ne laser, which are both nice and obvious and relatively reliable (for physics demos). We took a few measurements and used them to find the wavelength for the microwaves and the slit separation, d, for the laser experiment.

We also used the travelling microscope to measure the slit separation, using a flexi-cam and projector to show both the view down the scope and the readings on the Vernier scale.

Optimistically, I decided to try the same set up for Thin Wedge Fringes and Newton’s Rings – demos which are not so nice and not so obvious and, as I’ve found in the past, can be awkward to set up. Worse still, they must be observed through a microscope, ideally a travelling microscope to allow measurements of fringe spacing to be taken.

The thin wedge fringes worked pretty well and we measured the fringe spacing, using it to calculate the thickness of the wedge. And it all worked!

Continuing to ride my luck, I had a go at Newton’s Rings, using our ancient, somewhat chipped Griffin apparatus. After setting it up, I had a look through the eyepiece and, to my very great surprise, saw the brightest, clearest Newton’s Rings fringes I have ever seen.

To my further surprise, it all looked great through the flexicam-projector, so much so that I took a picture and tweeted about what I’d been doing. One reply, from John Burk (@Occam98) asked how I’d set it up.

So, here goes…..

The images below show how the flexicam was connected to the travelling microscope, using a collar to align the camera and eyepiece lenses, and in turn connected, via the S-Video input, to a Sony LCD projector.

It’s a very rare physics lesson where all of the experiments work, let alone first time. Luckily, when I needed to get through a lot of experiments to gather up the loose ends of the unit, that’s exactly what happened. After all the effort of getting all the apparatus together and set up, getting such excellent images for Newtons’ Rings was a great way to finish my lesson, and coincidentally the Advanced Higher course.

All downhill to the exam now…..

All Hands to the Pumps

On Wed 29th Feb, with our senior school out on exam leave for their prelims, and a clear desk (not sure how that happened, but it did) I dipped into my twitter stream and saw this tweet from Glen Gilchrist -

I've just blogged: PLNs and peer collaboration http://t.co/8RuTVQXN #mathchat #scichat #ukedchat

02/29/2012 3:24 pm via Glen GilchristReplyRetweetFavorite

@mrgpg

Glen Gilchrist

Glen’s post on PLNs and peer collaboration, details how he and Alexavier Fareheed made the journey from tweets to emails to collaboratively authoring their book, ‘Beyond the Mean‘, using Google Docs in just 10 days.

This post chimed very strongly with an idea I’d discussed in the past with Physics teaching members of my twitter PLN – given dwindling school budgets, and the inherent flaws of static printed texts about fields which are continually developing; why don’t we just write our own ‘virtual’ textbooks?

For about 6 years I’ve been a subscriber to Scotland’s largest and most vibrant subject-based email forum for teachers – The Institute of Physics ‘SPUTNIK’ . The forum has over 600 members from about 900 physics teachers in Scotland, and on a typical day may have 20 or more posts with members sharing links, seeking help, floating ideas and debating the issues of the day. A recurring topic on SPUTNIK has been the new certificate courses coming on stream over the next few years as Curriculum for Excellence progresses, for which details have been released, bit by bit, from our examination board, the SQA.

In conjunction with SPUTNIK, our community is fortunate to have its own dedicated website for storing and sharing resources – SPTR.NET - which was set up and is curated by the mysterious Magic Physics Pixies. The Physics community has made a great deal of use of this, with many benefitting from those generous members making their materials for new CfE units of work and the new Higher Physics course available to everyone.

After reading Glen’s post last week, I posted a short message on SPUTNIK, floating the idea of using a similar approach to producing texts for the new National 4, National 5, Higher and Advanced Higher courses. There were a few positive responses, but nobody seemed to be ‘biting’.

Being a bit busy with prelims and coursework for a few days, I wasn’t able to do anything more with the idea until this week, when I decided to use Google Forms to canvas opinion on the idea a bit further and get a few folk to sign up to contribute.

It’s early days yet, but about 20 people have signed up to contribute in the first few days. Hopefully we can gather enough people to get things organised next term and start writing in the summer holidays.

In an effort to get full coverage and ensure quality, it seemed that the project should break down as follows -

• minimum 3 contributors per unit
• one proof-reader/editor per unit, overseeing contributions
• one proof-reader/editor per course, overseeing all units

WiiMotes for Physics Experiments

I’ve been trying to get to grips with WiiMote Physics in the last week or so. It is a piece of free software which utilises Bluetooth connectivity on your PC to receive data from a Wii gaming controller.

A WiiMote has three accelerometers and an infra red camera inside. Using these it takes 100 measurements from each detector per second.

Physics Summer School – Day 2

Friday morning saw us leave Erskine early for a visit to the Physics Department University of Strathclyde. Here we were shown around the first-year labs, seeing experimental set ups used by students for finding -

• speed of sound in air using tuning forks and resonant air columns
• wave speed for wave on a string, using electric guitar and a device called an iRig hooked into an iPod
• Young’s modulus
• Focal length for a thin lens & refractive index for varying wavelength of light

After coffee we took a tour around some of the research labs, seeing a variety of things that, I must honestly admit, I really struggled to understand.

• One group are using very high power laser pulses in a variety of ways, including to accelerate sub atomic particles, on a scale of tens of metres, rather than the tens of kilometres required at CERN. There are hoped to be many practical spin offs, particularly in the fields of medical physics.
• Another group uses lasers to cool matter to very low temperatures, removing energy from atoms until they reach a temperature in the region of 10 nK (just 10 billionths of a kelvin above absolute zero). At such low temperatures the sample changes to a peculiar state of matter known as a Bose-Einstein Condensate (BEC). The experiment is set up using CCTV cameras to observe the sample, which produces an image very similar to an interference pattern when the BEC state is achieved.

Unfortunately the presence of a dozen bodies in the confined space of the lab made it very difficult to lower the temperature sufficiently – we were radiating too much heat!

After lunch we left Strathclyde University to visit Whitelee Wind Farm where we were shown the visitor centre and given a tour of the site. Despite having visited Whitelee many times myself, I have never been on the tour, which takes visitors on a short trip around the wind farm in an all-electric bus. The tour was highly informative about the windfarm in all respects, dealing with the design and function of the turbines, their installation and maintenance and the environmental issues surrounding the facility. Despite the conditions we all stepped outside to take a look at one of the turbines up close, before returning to the visitor centre to warm up.

After dinner Stuart Farmer showed us a simple, but brilliantly effective, exercise in handling uncertainties. Involving no more complex a measuring instrument than a ruler, some plastic cups and marbles, this activity gives an excellent insight into the real significance of uncertainties and could easily be used with pupils at all stages. I will certainly be using it with my new AH Physics class when the senior pupils return from study leave.

Physics Summer School – Day 1

For the last few days I’ve been fortunate to have been in Erskine, attending the SSERC/Institute of Physics Physics Summer School – a residential CPD event for physics teachers from all over Scotland.

We started on Wednesday evening with an icebreaker session after registration and dinner. Armed with a small video camera we conducted 30 second interviews on each other at the behest of Bob Kibble.

Thursday morning began with a session from Miles Padgett from the University of Glasgow on ‘Creativity in Science’. Using Edward De Bono’s ‘Thinking Hats’ as the basis for individual thinking and group discussion approaches to planning and problem solving, my  group was charged with the task of ‘re-inventing’ the game of chess. Given a constraint of having chess pieces on both sides being in one colour only, we used the techniques to formulate the idea of a ‘smart’ chess set with pieces able to assist players in a variety if ways. The functionality of such a chess set would, we concluded, be of benefit to players using two coloured sets, potentially helping players to learn to play chess better, leading them to improve their game. Just like roof tiles for one-armed roof-tilers.*

The next session, lead by Gregor Steele, was on using Wii controllers for motion analysis, using free software and the bluetooth connectivity of most PCs in conjunction with the three-axis accelerometers and IR camera position sensing capabilities of the Wiimote. The system proved relatively simple to set up and run and worked well for logging acceleration and displacement for simple harmonic motion and central force and rotational period for circular motion.

Next there was a short Blue Peter style make your own spectroscope activity, using an old CD and plastic box, from MUTR Mindsets. Armed with our spectroscopes, we popped outside to see if we could spot the Fraunhofer absorption lines in the spectrum obtained from sunlight. There were definitely some dark lines present, but after repeated observation, using a number of spectroscopes and some discussions over their nature, we concluded that we were most likely seeing the tracks on the CD itself.

The image on the left is of the spectrum obtained taken using my camera phone. Despite the poor quality of the image, the dark lines shown seem a little too regularly spaced to be Fraunhofer lines.

After this, we went on to have a look at a variety of activities using web cams to detect near infra red radiation. Having successfully butchered a brand new web cam by removing the IR filter, we set about looking at a variety of objects emitting near infrared, but no visible light. The two PCs in the image on the right are showing a heating element in the visible range (left) and in the IR range (right). The element was not glowing at all in the visible, but gave a bright IR signature.

After dinner we were whisked off to Glasgow City centre for a ‘Science Walk’, starting in George Square. Carol Trager – Cowan from Strathclyde University was our guide showing us, and telling the stories of, the statues of James Watt and Thomas Graham, the standards in the square and the Ramshorn Churchyard.

Signalling Challenge

image from www.athropolis.com

As an end of term activity I thought I’d have a go at getting my S3 class to try some old fashioned telecommunications methods, with an outdoor learning/group work/challenge slant.

So we’ve got 4 teams, sending the same message – ‘The quick brown fox jumped over the lazy dog’ – by four different methods -

• International Flag Code (on A4 sized flags)
• Morse Code (using a signal lamp)
• Semaphore (using two A4 sized flags)
• SMS text (using the pupils’ own mobiles)

The challenge will take place over the full length of the school campus – a few hundred metres – and the messages being sent will be both timed and checked for accuracy.

To try to even things up a bit the SMS team have to relay their message between all 4 members of the team, as it seems pretty obvious that they’ll be quicker.

To provide the flags for the flag code I made up a powerpoint, which when printed out double sided as slides gives the pupils flags with the letters on the back. The powerpoint is available on my ‘S3 & 4 Work’ page.

Results will follow….