Tag Archives: Advanced Higher

Perimeter Institute – EinsteinPlus 2016 – Day 2⤴

from @ stuckwithphysics.co.uk

Day 2 of EinsteinPlus 2016 saw the group formally welcomed to the spectacular Perimeter Institute building after an equally spectacular breakfast. (There are two excellent bistros at PI, which provided the group with a fabulous range of meals over the week long visit. I'd say more, but there'd be a real danger of this becoming a food blog...)

The morning session was split into two -

  • Cosmology - this used an existing PI activity 'The Signature of the Stars' from their educational resource on 'The Expanding Universe' - using diffraction glasses observations were made of line spectra from a variety of gas discharge lamps. These spectra are used to identify the elements present in stars, in the Milky way and in distant galaxies. The spectra of light from distant galaxies shows the same spectral lines as stars in our galaxy, but the lines appear in slightly different positions, with longer wavelengths. This effect, known as Red Shift, occurs because the galaxies are moving away from us, and each other, at high speeds. Measuring the red shift for a galaxy can be used to measure its speed, which relates in turn to its distance from us. This effect was first observed in the early 20th century and used to formulate Hubble's Law - which states that not only is the universe expanding, but the further away from us a galaxy is, the faster it is moving. The activity includes data allowing the red shift of a range of galaxies at different known distances to be used to find their speeds. This data is then plotted it give a graph representing Hubble's Law, which gives an approximation of the Hubble constant and can in turn be used to find the age of the universe.

  • Gravitational waves - this used a newly developed activity based around the recent detection of Gravitational Waves at the Laser Interferometer Gravitational Wave Observatory (LIGO) facilities in the USA. The facilities use extremely large scale (~4km) laser interferometers to measure incredibly small expansions or contractions (~10-19 m - 1000 times smaller than the diameter of a proton) of the devices which occur when gravitational waves pass. There are many areas of physics and engineering involved in the development and operation of the LIGO detectors, from the solutions to Einstein's General Relativity which predicted the existence of Gravitational waves, to the intricate suspension of the mirrors sued to improve the sensitivity of the detectors - developed at the University of Glasgow. The activity centres around the properties of waves, and their behaviour when they undergo reflection - beginning with demonstrations of mechanical waves using a slinky. Observations of phase change upon reflection were developed upon and related to the operation of the interferometers at LIGO. These ideas were utilised in a hands on activity to simulate the paths of the laser light used at LIGO in order to find the nature of the light detected when the device is unstretched (no gravitational wave) and stretched. This task offers an excellent opportunity to link this part of the Advanced Higher physics unit on waves to a context which involves real, cutting edge physics.

LIGO unstretched

LIGO stretchedAfter lunch, followed a two more sessions -

  • Neutrino Detection - another new activity, this is based on the Nobel Prize winning work of Professor Art McDonald and his team at the Sudbury Neutrino Observatory (SNOLAB). The session began with an overview of the production of neutrinos in the sun and the difficulty in detecting these particles - the 'Solar Neutrino Problem'. The session continued with a description of the facility at SNOLAB and a hands on task modelling the detector using marbles, cardboard boxes and a baking tray. There was a great deal of discussion about this task, and the nature of the model to describe and explain neutrino detection. Consequently there was a shortage of time for the remaining tasks, dealing with real data from SNOLAB and the theory of 'neutrino oscillation'.

  • Dark Matter - this session used the 'Dark Matter Within a Galaxy' activity from 'The Mystery of Dark Matter' materials. The activity begins with a revision of the basic rules for circular motion and gravitation, using a range of data to find and plot the orbital speed of a star against its radius from the centre of its galaxy. These values, calculated from classical theory, do not compare well with observational data - implying that there must be more mass in these systems that we can not detect - Dark Matter. Whilst the part of the underlying physics of this task, circular motion, is beyond the scope of the Higher physics course in Scotland, it might be fair to use this as a practice data handling task which could be used to exemplify and reinforce the very brief mention of Dark Matter in the 'Our Dynamic Universe' unit.

The final session of the day was a keynote presentation delivered by Professor Avery Broderick from the University of Waterloo on the Event Horizon Telescope (EHT). This program uses nine existing telescopes across the globe and applies a technique known as Very Long Baseline Interferometery (VBLI) to improve the resolution at which images of very small objects can be made.

It is hoped that by improving the resolution for existing telescopes and including planned future telescopes in the gathering and processing of data, the EHT will obtain the first direct images of the event horizon for a black hole in our galaxy. Recent observations in the constellation of Sagittarius are thought to indicate the presence of a black hole with a mass around 4 millions time that of our sun. This black hole is of the right size and at the right distance for the EHT to be able to make observations that will allow an image to be obtained in the next few years.

The data gathered and images obtained by the EHT will allow for further testing of Einstein's theory of General Relativity, and provide a greater understanding of phenomena such as black hole accretion and plasma jets.

After this presentation and another excellent meal the group was offered a tour of the Perimeter Institute building, offering an insight into how the facilities have been designed and developed in order to attract and facilitate the work of some of the world's foremost theoretical physics (not to mention a very large number of teachers and students).

A selection of images of the building will be included in a gallery as soon as I figure out how to make it work...

 

Newton’s Rings⤴

from @ stuckwithphysics.co.uk

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…..

Griffin Newton’s Rings apparatus -
plano convex lens placed convex side down on glass plate
Beam splitter (sloping glass plate) reflects light from sodium lamp (in blue lamp holder) down on to lens
Travelling microscope above for viewing interference pattern through beam splitter.

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…..

WiiMotes for Physics Experiments⤴

from @ stuckwithphysics.co.uk

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.

This makes it an ideal device for measuring many types of dynamics effects in physics.

I first used this capability of the WiiMote at the Physics Summer School using the accelerometer and IR detection for logging the simple harmonic motion of the WiiMote oscillating as a mass suspended from a spring, and swung on a string as a pendulum.

As my Advanced Higher Physics class have been working on the rotational mechanics part of the course I thought I’d try to do a qualitative measurement of centripetal acceleration against angular velocity using an air bearing turntable.

Placing the WiiMote radially on the disc, it should measure the centripetal acceleration in ‘g’ in the +Y direction. The angular velocity isn’t as straight forward, being calculated from the period of revolution. The period is measured using the IR detector which ‘sees’ a lamp as it passes each revolution. This gives a regular peak on the trace for the IR detector.

At least, that’s the theory. In practice its been somewhat trickier to achieve. There have been a few foibles to overcome -

  • getting the WiiMote to connect to the PC via Bluetooth
  • getting the software to show a reading from the IR detector
  • geting the IR detector to ‘see’ the lamp
Luckily, I have the brilliant support of the  Scottish Physics Teachers Network (SPUTNIK) an email forum, that has been great (as always) at offering help when I’ve detailed the problems I’ve had.
It’s been a steep learning curve, but I think I’ll be able to get some measurements done with my AH class next week. Fingers crossed….

Thinking Differently to Motivate Independent Learning⤴

from @ stuckwithphysics.co.uk

Inspired by a session at the Physics Summer School, I decided to try a ‘creative thinking’ exercise with my new S6 Advanced Higher pupils.

Giving them the theme of ‘Successful Learners’, I asked them to spend a couple of minutes, individually and in silence, writing down all of the things they thought necessary for learning to be successful.

Having done so, I put them into groups to discuss their individual lists and compile a ‘super list’ for their groups. Each group was then asked to give 3 or 4 items from their ‘super list’.

This was scribbled up on the board and discussed as we went.

 

As expected, the lists were very similar for each of the groups, but there were some responses given by only one group – ‘time’, ‘confidence’ and ‘classmates’ (hence the underlining).

The aim of this part of the task was to reinforce ‘accepted wisdom’ before turning things around with one of three ‘what if..?’ scenarios for each group.*

  • ‘what if there were no books?’
  • ‘what if there was no course?’
  • ‘what if there was no teacher?’

This time they were asked to come up with strategies for overcoming these apparent difficulties. Again the groups were encouraged to spend some time silently coming up with their own individual ideas before discussing in their groups. Once they had discussed their ideas, we put together another summary.

Again, the responses were discussed as we compiled the list of ‘solutions’ it became obvious that all of the solutions pointed towards aspects of independent learning, none of which were in any way specific to Physics. It was also obvious that even in our true circumstances, where we do have books, a prescribed curriculum and a teacher that these ‘solutions’ would still be of benefit in ensuring they learn successfully.

This got me onto my hidden agenda – making extensive use Glow to achieve many of these goals.

The plan is for my pupils to compile their own ‘textbook’ in the form of a class Glow Wiki; to make use of materials in our Glow Learn resource library; to use the class Glow forum to discuss difficulties, both asking for help and providing assistance to others; using Glow blogs to record their progress through their AH investigations; adding links to ‘good’ web sites to the Glow group and anything else that occurs to me, or them, over the next few months.

I’m also very keen to push SCHOLAR – Heriott Watt University’s VLE – and get as much of their data handling for experimental work performed using simple spreadsheet techniques, rather than laborious manual analytical techniques.

Suffice it to say, my new class seem a little worried at this approach, some admitting they would be out of their comfort zones. But they seemed to recognise the potential benefits to them of gaining these skills and adopting these attitudes. And hopefully they fancy stepping up to the challenge.

If I’m honest, I am a little worried too. I may have bitten off more than I can chew. I may need to spit a bit out. I might also choke.

That said, I’m not short of support, despite being almost the only ‘Glow guy’ in my school, I’ve also got my guardian angel at the LA, and my amazingly helpful and knowledgable PLN on twitter to fall back on.

I will be blogging about this project on a different blog – the class Glow blog.

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*[On the Physics Summer School Creative Thinking session we were given the example of 'what if a roof tiler lost an arm? how could he still do his job?'

By adding a captive nail and a sticky pad to the back of each tile, he could probably manage to do the job, but such additions make the job significantly easier for uninjured roof tilers. Thus, the solution to the apparently absurd 'what if?' has real benefits for all.]

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