We all love Seasick Steve, the former tramp made famous when Jools Holland got him to play his blues on the 2006 Hootenanny TV show. One of his favourite instruments is the one-string guitar, known as a “Diddley Bow“.
A great lesson in the physics of sound can be had at all ages and stages by introducing the idea that to make a sound, something has to vibrate. Starting with twanging rubber bands and rulers, investigating the effect of changing tension and length, pupils can be set a great project to do at home – build your own diddley bo! A friend did this with her primary 5/6 class quite recently. Here are some of their instruments, and the master himself:
You can find more info on how to build your own over at One String Willie’s.
On Tuesday evening, I went with a number of other Physics teachers to the Royal Observatory, Edinburgh, for an evening of information and practical observing to help teachers thinking about putting on Astronomy events in their schools.
We were given a history of the telescope and links to some very useful and interesting resources, which I thought you’d like to share:
Heavens-above.com (type that carefully) provides detailed information for observing all kinds of things in the sky from the International Space Station, Iridium Flares and of course, stars, planets and galaxies
Stellarium is a free open-source planetarium for your computer (Mac, Linux or Windows) which shows a realistic sky for your location
Finally, as well as useful tips for a successful observing evening (a hat, a red light, thinking about safety were the main ones) we were given a book recommendation: The Complete Idiot’s Guide to Astronomy.
My Advanced Highers will be joining some others on a visit to the ROE in November.
Our technical people have made us a great new resource: a tube which is drilled with tiny holes. When we push gas through the tube and light it, we get a long line of little flames. Now, when sound waves are pushed into the tube through a loudspeaker, the resulting pressure waves inside the tube produce visible sound waves in the flames. This is a Rubens Tube and it’s brilliant.
This week we have almost completed the theory part of the first unit in the Higher Physics course. We have considered uncertainties and how to calculate them before getting down to some real practical physics.
At the end of this first unit, students are required to have completed a small practical investigation into something related to Mechanics and Properties of Matter. This is called “learning outcome 3″ or LO3 for short. We are conducting the practical component of the LO3 this week. Some are investigating the gas laws, others, kinematics.
“The only source of knowledge is experience” Albert Einstein
Einstein’s quote is rubbish, of course. But he has a point – from practical experience, you can really set your knowledge on solid foundations. This is the principle of having a practical element to teaching physics, where such facilities are available.
In the lab, keep your thoughts clearly on the basic principles of scientific investigation that you have already learned: only change one thing at a time, for example, controlling all other factors. Record exactly what you see: for example, the numbers on the voltmeter (indicating pressure indirectly) in the picture should be recorded with the minus sign. If a fire-breathing dragon should walk by your experiment, record the fact and comment on its relevance to the validity of your findings when you come to write up your report.
Your practical activity may be completed as part of a team: some measurements are difficult to do on your own. The report you write on the experiment, however, must be entirely your own work. There is a clear set of performance criteria which your report must meet and you must meet all of them for it to pass as satisfactory. You can find these criteria in the SQA arrangements documents, pages 26-28. There is a simple summary of what your report should include here.
Once you have written the first draft of your LO3 report, before you submit it for marking to your teacher, listen to this podcast tutorial: it takes you through the checklist of essential things your report should have. Enjoy your practical work: here’s another quote to think about, this time from Karl Marx:
“Practice without theory is blind. Theory without practice is sterile.”
It can be tricky getting your head around the Advanced Higher Physics investigation, otherwise known as the “fourth unit” of the course. There’s a great deal of the unknown about it, as you are required to choose (or worse, have chosen for you) an investigation of suitable complexity for the assessors when they read your report, quite possibly before you have covered the physics in the course. There’s also the small matter of the mysterious day book. Let’s take a look at what you have to do for this part of the course.
Read the guidance
Start off with a look at the course guidance produced by the SQA. Here you will read that the investigation is:
a piece of individual research undertaken to prove that you can … research a physics topic … design and plan experiments … carry out experiments safely and accurately to collect data … process and present the data … evaluate … produce a written report
The report is assessed by the SQA examiners. Your school will assess your day book and the investigation itself, including your recording of the data.
There are three phases to the investigation: planning, execution and reporting. Read the course guidance first, before thinking about which investigation you want to do, then set about planning it. Don’t be one of the entries without the basics taken care of: read the guidance again and again as you progress.
Start your day book
The day book is simply a kind of running record of your activities as you conduct your investigation. Your school may give you a hard-backed lab book to use for this, but you are not constrained to this format – loose leaf is OK, for example. The photo shows part of my library shelf containing the day books I have kept, which shows you that I quite like the A4 hard-back type.
Day books
Begin writing your day book entries as soon as you start thinking about which investigation you are going to do. Write down, date and reference everything you do in relation to the project. I personally number my pages and you should too. A margin at the side of the page is also helpful for comments and provides a place for your teacher to put a date and signature every time he or she checks your day book. It is your responsibility to ensure it is regularly checked: at least once a week is reasonable until the investigation report is finished.
Some people worry about copyright when putting things into the day book – it’s perfectly OK to paste a photocopy or digital photo of a text book page describing a procedure into your day book if it’s relevant to the investigation. Don’t forget to fully reference all of your sources of information and to record even informal discussions with teachers, technical or university staff who might be offering advice and support. Referencing means stating exactly where the information came from: details of a book’s author, etc., or the address of a web page and when you accessed it. Record these details in your day book as you find the information – you’ll need them when you write up the report.
Choose an area of interest
There is almost no limit on what your investigation is about, provided that it meets the basic requirements of the course. Students sometimes just plump for something they have read about on a forum somewhere (see, for example, here, here, here or here) or really push the boat out and do something outstanding with a hook into their degree aspirations. My advice would be to generally keep it simple and make sure your report is as good as you can make it.
A few years ago, Linlithgow Academy made a list of suggestions for the investigation available. You can find a copy of that list here. There is also a relatively new site used by physics teachers in Scotland to share resources: the AH investigations pages, with suggestions for investigations, can be found here.
Things to watch out for
Firstly, don’t panic. This isn’t rocket science. OK, it might be rocket science but it’s doable rocket science and you not only are allowed to seek support and guidance, you are expected to do so.
Secondly, don’t get complacent. Start now. Read, dive into the text books and experiment books: see if there’s a copy of Tyler in your lab. Get on with it. Locate the equipment you need. Talk to people. You probably have prelims after Christmas and the exams will follow oh so quickly after that. You don’t need to be burdened with the investigation at that time (although this is often when they are done).
One other area you will need to pay close attention to is uncertainties. Read the guide downloadable from the LTS website. Your day book does not have to be exam-perfect in terms of number of decimal places and so on but keep in mind the golden rule that as a scientist, you must record what you see: fairly, accurately and without bias.
Getting help
So, what help can you get? Apart from the SQA website, there are a number of good sources of help in getting your investigation off to a good start, and in keeping you going if things get a little tricky. The Science 3-18 website, run by the Scottish Schools Equipment Research Centre (SSERC), has some resources related to the investigation here, including some specific notes on investigations using radioactive sources. SSERC also offer support to students directly – whether trouble-shooting or making equipment available or just good solid advice. I happen to live not far from SSERC, so arrangements can be easily made.
Our local universities (specifically Dundee, St. Andrews and Heriot-Watt) all offer support for the investigation. Glasgow University also offers an Advanced Higher Helpline, an e-mail advice and support service which aims to provide the following support:-
advice on possible experiments to develop or complete an investigation
advice on the treatment of uncertainties in more complex situations
a booking facility for access to investigation enhancement experiments within the department or the possible loan of equipment
help to understand “unexpected” results or systematic errors
To use the Helpline contact Peter Law, the Advanced Higher Support Coordinator, at the following address (remove the “NOSPAM” first): AH-HelpNOSPAM@NOSPAMphysics.gla.ac.uk
Finally
The SQA’s External Examiner’s report for 2008 indicates that the average mark for the investigation was just under 14/25. The “something outstanding” mentioned above got 25/25.
A small bunch of us went out on a trip to the bright lights of Kirkcaldy today to take part in a nice interactive programme of physicsy things. We got to learn about the applications of Lasers; to operate laser tweezers and move 5 micron (that’s a thousandth of a millimetre) marbles; see total internal reflection and refraction; we listened to mad scientist Gill Arbuthnott tell us about mad creatures and even madder scientists; and we got to program robot buggies using light and touch sensors and the genius of our own minds. We had fun!
I thought I’d try and make my own spectroscope. A spectroscope allows you to split up light from a source into its separate wavelengths. Scientists use this instrument to find out what chemical processes are taking place inside distant stars – every element has its own “signature” and from the spectrum of light given out by a reaction (the emission spectrum), you can tell which elements are involved. A quick search on the web found some ideas, and this is how I made my own spectroscope.
I started with a cardboard tube, razor blades, scissors and scalpel and some duct tape. Are you thinking of trying this yourself? I need not warn you to be careful with sharp things. They cut, you bleed and then you die. Be careful. Really, get help if you are little or unsteady with your hands. Better still, don’t do it at all unless you’re prepared for any consequences.
Scratch the paint away from the edge first.
Anyway. The cardboard tube was used to send me some posters for my classroom, but I guess any tube will do. It doesn’t have to be as big as this one. We need a diffraction grating for the eyepiece end of our spectroscope.
Lift off the paint with duct tape
CD’s and DVD’s have fine lines in them which are perfect for this but they usually have one side painted – the inside is mirrored to make the CD player able to read the data on the CD. We need to remove this paint and the mirror surface. Start by scratching a little of the paint away from near the edge. Then use small strips of the duct tape to lift the paint off the CD or DVD.
Pretty rainbows in my CD
You can use clear sellotape for this, but the glue on the duct tape is stronger and makes it much easier. Work all the way around the CD until it’s clean and you should be able to see the rainbow effect from the lines in the surface by holding it towards a light. Later, you are going to cut the CD with scissors. It might be a good idea to warm it up – on a radiator or by placing it in hot water for a while to make it easy to cut without shattering or slipping.
A sharp slit made with a razor blade
Next, we need to make the objective end – for this, we need a fine slit: this can be achieved by cutting into any material but I am going to be using two edges of a razor blade and fix them a short distance apart. My tube came with little plastic inserts each end to keep the posters safe. With my scalpel, I cut an opening in one of them and fixed the razor blades carefully with duct tape. Remember to put something underneath whilst you are cutting with the scalpel, so you don’t damage your lovely kitchen surfaces.
The finished slit in position
Before fitting the slit into the tube, I painted it black (actually, I used a permanent marker pen) to reduce the light coming through the end of the tube except through the slit itself. I made sure that any sharp edges were well covered with duct tape and that it all fitted securely inside the end of the tube.
Cutting the CD to fit
Now, I cut a circle from the CD to fit securely into the other end of the tube to provide the diffraction grating for the eyepiece. The grating has to fit such that the lines on the CD go in roughly the same direction as the slit at the objective (far away) end of the spectroscope.
The CD eyepiece
You might need to try it – point the end with the slit towards a household lamp and rotate the eyepiece until you get the best effect. Then, tape it securely in place and – bingo! – your very own spectroscope is complete and ready for action.
One more word of warning, please don’t point a spectroscope or anything else in such a way that you look directly at the sun. Your eyes may be permanently damaged as a result. Just be careful, but enjoy a little practical physics. I’ll leave you with two results – one, a spectrum I obtained by pointing the spectroscope at my kitchen lamp – it’s one of those new low-energy lamps and clearly shows the emission spectrum from the phosphor coating. The second image is a continuous spectrum obtained from our own star.
