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New Recommendations for the Safe Use of Laser Pointers

David Gervais, Chair STAO Safety Chair

STAO’s Safe on Science booklet is a great resource for teachers and is used as the standard for safe practices by many school boards in Ontario. It presently states that only class 1 and 2 lasers should be used in the classroom. This bans almost all laser pointers from your classroom. A recent OAPT Newsletter article questioned why class 3R lasers (most regular laser pointers) are not accepted. After carefully reviewing the literature and holding extensive discussions, STAO has decided that laser class 3R should be added for recommended use in schools. The Safe on Science booklet is being revised and will be completed by March 31. This will be sent to school boards in the province. Read More...

Improving Writing and Thinking in Physics: Writing with the 4 Cs

Roberta Tevlin, teacher Danforth CTI, editor OAPT Newsletter roberta.tevlin@tdsb.on.ca
Edited by Tim Langford

Are you getting frustrated reading answers that ramble on and don’t make much sense? Does it look like your students are writing everything they know about the topic in the hope that some part of it answers the question? Writing with the 4 Cs is a teaching technique to improve writing and thinking. Read More...

Bringing the Wonder of Discovery Back into the Classroom

Christine Hudecki, Teacher Our Lady of Lourdes Catholic High School
Christine.hudecki@wellingtoncdsb.ca

The grade 11 and 12 physics curriculum, I find, is heavy with concepts and formulas. Every day or every other day a new idea is presented, different formulas introduced and a fresh set of problems need to be solved. One of the reasons I liked science and enjoy teaching science is that it is a ‘doing’ subject. It has the potential to get students out of textbooks and in front of equipment. They can learn skills and exercise their problem solving abilities.

In effort to put more ‘doing’ into the grade 12 Light unit, I looked at the polarization lessons. There are some strange things that happen with polarizing filters and most often I would have the students play with the filters after we learned the concept of polarization. It occurred to me that I should flip this order. Read More...

Cheap and Safe Solar Observing for Grade 9 Astronomy

Roberta Tevlin, OAPT Newsletter Editor, Teacher Danforth CTI
roberta.tevlin@tdsb.on.ca
Edited by Tim Langford

It is difficult to get students to make astronomical observations when you live in a large city with lots of light pollution. However, there is one object that all of your students have seen, but probably not observed carefully — the Sun! I start my grade 9 astronomy unit by having my students observe the shadows formed by Sun. Read More...

Demonstrating Polarized Interference

Roberta Tevlin, OAPT Editor, Teacher Danforth CTI
Rolly Meisel, OAPT Photographer
roberta.tevlin@rdsb.on.ca

The interference of light is a very important concept in senior high school physics and has been for a long time. The polarization of light used to be a minor topic but has become more and more important over the last couple of decades because of its use in LCD screens and 3-D movies and because it is possible to get a cheap class set of polarized filters. This article describes a demonstration that combines polarization and interference. Read More...

Diffraction and Resolution

Phillip Freeman, Teacher, Richmond Secondary School, Richmond, B.C., Executive Member at Large BCAPT
freeman@sphericalcows.net

The diffraction of light limits the resolution of optical systems. This is relevant in a number of real world cases, from the reason you can’t actually zoom in infinitely to read the license plate of the get-away car on the crime drama, to the limit to how small an insect a bat can ‘see’ with echolocation to the current plans for the Event Horizon Telescope. It is possible to observe single slit diffraction and resolution directly with very simple equipment. Read More...

Building a Michelson Interferometer, Part II

Richard Taylor, Merivale High School, Ottawa
(see also
mrtaylorspace.wordpress.com)
richard@teya.ca

In the last episode, I had received the main parts of a Michelson Interferometer (the mirrors) and had roughly set them up using Lego stands. In the past couple of weeks I have been working on making a more stable and adjustable platform for this interferometer. Read More...

REVIEW: Three Short Videos of the Double Slit Experiment

Roberta Tevlin, OAPT Editor, Teacher Danforth CTI
roberta.tevlin@tdsb.on.ca

The double-slit experiment is one of the strongest pieces of evidence for the wave nature of light and it is also the best place to start to explore the key concepts of quantum physics. By this point, most teachers in Ontario are familiar with the great, free teaching resource from The Perimeter Institute of Theoretical called The Challenge of Quantum Reality. If you haven’t got yours yet, you should! Three short, on-line videos are now available as an addition to the resource. Read More...

Building a Michelson Interferometer

Richard Taylor, Merivale High School, Ottawa
(see also
mrtaylorspace.wordpress.com)
richard@teya.ca

My school has had a Michelson Interferometer for many years, and I always show it to my grade 12 students to help explain the Michelson-Morley experiment - the one that showed that the speed of light does not depend on the motion of the observer. I showed this interferometer to some other Physics teachers on the February 2016 PD day in Ottawa. They were very interested and wanted to show their students. So I thought I would find out if I could build a similar and very inexpensive interferometer. Read More...

Review: Eureka Talks: University of Ottawa

Richard Taylor, CAP Councillor for Affiliates, Teacher Merivale High School, Ottawa
Richard@teya.ca

The University of Ottawa’s Physics Department has initiated a lecture series they call “Eureka Talks”. The first of these talks was given Saturday January 30, 2016 by Sir John Pendry of Imperial College, London, on the topic of metamaterials and invisibility.

Sadly, I must inform you that Harry Potter’s invisibility cloak is still not available. Even worse, if Harry was invisible, he wouldn't be able to see anything — he’d be in total darkness, with all the light rays bent around him and none going into his eyes! Read More...

Gravity Waves: The Fast Track to the Best Resources

Margaret Scora, Mhona Russell, James Ball and Roberta Tevlin

The announcement that LIGO has detected gravity waves may have you scrambling to answer your student’s questions. This news connects to many topics in high school physics including waves and vibrations, interference of light, changing models of science and the analysis of data - especially the problem of signal to noise ratios. Many teaching resources have been suggested (listed at the bottom) and these have been examined to select which are the most useful for high school physics teachers. The selected videos are well-scaffolded and paced. They make good use of animations, physical models and analogies and showed a wide diversity in the people interviewed. Demos and activities were selected which require minimal prep time and cost for the teacher and which provide active-learning experiences for the student. Read More...

An Experiment Involving Heisenberg’s Uncertainty Principle

James Ball, OAPT Membership Chair, Physics Teacher, John F. Ross C.V.I.
James.Ball@ugdsb.on.ca

The Heisenberg Uncertainty Principle is a very abstract concept for most high school students and teachers. This lab activity is a simple variation of a single slit diffraction experiment. It clearly shows that defining the location of a photon (by passing it through a slit) increases our uncertainty about its momentum. Read More...

Pointers about Laser Safety

Roberta Tevlin, OAPT Newsletter Editor, Physics Teacher Danforth CTI
Roberta.tevlin@tdsb.on.ca

There is a lot of confusion about which lasers we can and should use in our classrooms. Lasers are classified by power, spread of beam and a variety of other properties. The lower the Class, the safer they are. Read More...

Reversal of Spectral Lines

Dr. Eknath V. MaratheĢ, St. Catharines, Ontario

Spectroscopy has contributed to our knowledge not only of Earth but also of the Sun, interstellar space, distant stars and galaxies. The subject of spectroscopy began in the year 1666 with the discovery by Newton that when the Sun’s rays are allowed to pass through a prism, they produced a band of colours which he called a spectrum. In 1802, William Hyde Wollaston, (1766 – 1828, English chemist and physicist) used a narrow slit as a secondary source of light and observed dark lines in the spectrum of sunlight. Wollaston thought that the dark lines were natural boundaries between various colours of the spectrum. Read More...

Two Kinds of Polaroid Glasses

John Pitre, Department of Physics, University of Toronto
pitre@faraday.physics.utoronto.ca

When polarized light is discussed, polarizing plastic sheet filters are always mentioned. During manufacture, this material which contains
long chain molecules is mechanically stretched into sheets resulting in the alignment of the molecules. Electrons can travel along the axis of the molecules but cannot jump from molecule to molecule. When light is incident on a polaroid sheet, the component of the electric field which is parallel to the axis of the long chain molecules causes the electrons to move, and that component is absorbed; the component which is perpendicular to the axis of the molecules is unaffected. Thus, polaroid sheets have a preferred direction, or transmission axis, which is perpendicular to the axis of the long chain molecules. Read More...

Lasers: A Solution looking for a Problem

Roberta Tevlin, OAPT Editor, Teacher Danforth CTI
Roberta.tevlin@tdsb.on.ca
Edited by Margaret Scora

Lasers are quantum light sources and they are everywhere. But what is quantum about them? The PhET simulation is a great tool to give students a feel for the quantum process called stimulated emission. Read More...

Adding Colours

Alan Hirsch, Port Credit Secondary School

Having taught senior high school physics for more than 20 years, I had thought the chances of a student discovering something I hadn't seen before while performing a typical physics experiment were remote. Thus, when OAC student Karen Whiskin was performing measurements on the wavelengths of various colours of light and yelled out, "Hey sir, come and look at this!", I was not expecting to see anything new. To my surprise and joy, Karen's discovery was also a discovery for me. Using a single diffraction grating, Karen had observed the addition of light colours and had recognized that secondary light colours were being formed from primary light colours. Read More...

Reflections

George Vanderkuur, Malvern Collegiate, Toronto

A laser, chalk dust and right-angle corner made of mirror tiles show the retro-reflection of light from a corner cube mirror. (Safety note: use a low-power laser beam and take care to avoid directing the beam into the audience.) Students will also enjoy looking into the mirror and observing that the image of their face (or open eye) is always in the corner. Try this with one eye closed. Read More...

Colour Mixing the Economical Way

Bill Konrad, Chatham Kent Secondary School

I am sure that, in the schools of Ontario, the range of equipment presently in place to demonstrate colour mixing varies all the way from ray boxes with colour filters to expensive projectors specifically designed for that topic. Many of these may be effective but frequently one finds that the resulting colour is not exactly what theory predicts. For example, a blue light, a green light, and a red light projected onto the same area of a white screen may produce a “yellow” white or a “greyish” white. The demonstration described below gives excellent results and, in keeping with current budget constraints, is very economical. To carry it out, proceed as follows. Read More...
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