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Total Internal Reflection

Diana Hall, Bell High School, Nepean, Ontario

A fun example of total internal reflection can be created with an aquarium tank or similar transparent container filled with water. Students enjoy wandering around the tank with objects placed around on all sides including above and below. Sometimes you can see what you appear to be looking at and sometimes not. Students are challenged to draw ray diagrams to show why you cannot see certain objects but can unexpectedly see others from certain angles. One example is shown here. It’s definitely a good seed for discussion. Probably a good coffee table display for your parties too. Read More...

Classroom Demonstration of Spectra

Jim Hunt, Physics Department, University of Guelph
phyjih@physics.uoguelph.ca

The availability of large sheets of plastic replica gratings has greatly increased the ability to show spectra to classroom-sized groups and, in the process, put on a nice light-show. Read More...

Two-Minute Impromptu Demos

Ed van den Berg and Rosea van den Berg, University of San Carlos, Talamban Campus, Cebu City, Philippines
edberg@durian.usc.edu.ph

This article was excerpted (with the authors’s permission) from a longer article in The Physics Teacher (Sept. 1998, p.356-8).

What can we do to have clear and exciting lessons without a great amount of demonstration apparatus and hours of preparation each day? We present here a collection of small and quick demos that require no equipment beyond what is present in a classroom (chalk, chairs, students, books, paper, backpacks and their contents). Some are to prove something, but most are to illustrate, visualize, or simulate. These basic and well-tried ideas will stimulate students and revive the instructor who has spent a late night checking student papers. Have fun! 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...

Optics, Density, Holography, and Curve-Fitting

Dianne Ness, Humberside C.I.

Four demonstrations from Dianne Ness. 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...

Parallax and Images

T.J. Elgin Wolfe, Faculty of Education, University of Toronto

Parallax is the apparent motion of one object with reference to a second object caused by a change in position of the viewer. Involve the class in the following way to introduce this concept. Read More...

Virtual Image Formed by a Plane Mirror

T.J. Elgin Wolfe, University of Toronto

An interesting demonstration that makes use of the location of the virtual image formed by a plane mirror can be done with a black cloth, a small candle (about 2 cm in height), a dull dark opaque shield about 3.5 cm tall and bent at right angles, a large pane of thin window glass, two retort stands, 4 adjustable clamps, a 400 mL beaker, and coloured water. To highlight the beaker in the dim light, outline the outer edges (as viewed by the class) with masking tape. Read More...

Real Image Demonstration

Don Murphy, Sydenham High School

Many demonstrations can be made not just interesting but truly memorable by “setting up” the students a bit beforehand. A rather well-known demonstration involves a real flowerpot and a flower suspended upside down inside a box placed 2 focal lengths in front of a large concave mirror. The viewer sees an illusion of the flower being on top of the box but the image disappears when the viewer approaches too close. The apparatus on hand at our school for a similar demo is illustrated below, but in this case a real image of a light bulb is formed. Read More...
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