Since 2016 table top science demonstrations show simple experiments and “WOW-type” setups the children enjoy. The table top exhibits can be used to demonstrate topics and also to give the children to do hands-on experiments on subject matter that is in the Ontario Curriculum of Science and Technology.
Here is one of those demonstration tables. We hope you enjoy the experiments. Some are easily done at home with inexpensive materials.
Optics and Mirrors
The Manager of Education Programs, Colleen Brick, fourth from the left, and her team of leaders with the latest update of the Demonstration Table. The team interacts daily with the children in the After School Program at the Kingston Boys and Girls Club, Robert Meek Youth Centre, part of the Boys and Girls Club of Kingston and Area. For more information on the Boys and Girls Club Kingston and Aarea, go to the official website. Just click here.
At the front of the table two mirrors are set up as the pages in a book. The children can move the mirrors through an arc that includes angles of 120, 90, 60 and 30 degrees. In the photo the experiment is “open” at 120 degrees. In front of the mirrors is a piece of paper with a coloured drawing, There are three images, one the real object and the other two the virtual images.
Lets look at the range of angles with a toy sentry in front of the mirrors.
The largest angle in this experimental setup allows for an opening between the two mirrors of 120 degrees as this photo shows. There are one real and two virtual objects. The real object is in the front the other two virtual objects are in the back. They are the reflections, one in each mirror.
This is a 90 degree angle between the mirrors. Count the virtual objects: three virtual and one real object make four images together. The fourth in the back is in two halves, one half reflected in each mirror make a full virtual image if the mirrors are perfectly lined up at 90 degrees. The hinge between the two mirrors distorts the reflected image a bit.
Then below, the angle has narrowed to 60 degrees and we see …? Six objects.
Do you notice a pattern in the closing together of the mirrors from 120 to 90 to 60 degrees? At 120 degrees there were three objects, and at 60 degrees there were six objects. What is going on?
Multiply the degrees with the number of real and virtual objects and you get 360 in all cases. So with two mirrors facing each other at different angles you can calculate the number of reflections as the number of times the angle can be divided into 360. Try it: 60 degrees goes in 360, six times. So you would see six images.
If we had two mirrors opposite each other at zero degrees we would get a lot of virtual images, in fact so many that we could not count them, the number would approach infinite.
Well, take a peek in the Mirror Box.
The Mirror Box is the white square box at the end of the demonstration table. It has two mirrors opposite each other, one at the right hand side where you see the plywood backing and the red strip, and the other at the side with the green strip. The mirrors face each other at a distance that is equal to the sides of the box.There are three objects in the box and it is not so interesting when you take a casual look through the transparent acrylic lid on the top. Just a white box with three toy figures in it.
BUT lift the lid at the red stripe just about 2-3 centimeters so you can peek through the slit just above the red tape, and…WOW…
What is it that gets this excited WOW-reaction? Have a look at the photo below.
The three toy figures have multiplied to hundreds as far as you can see; the three real objects have hundreds of virtual reflected images. The two mirrors bounce the reflections back and forth, there is no end in sight.
Look a little longer and you see the same reflections of the toy horse and bird, but the toy guard, shows its face and then its back then its face and so on. It is as if it turns around at every full reflection.
Three Mirrors at 60 degrees; the Kaleidoscope
The optics demonstration table has a large kaleidoscope located between the two experiments we just discussed. It is the red tube with some spiral taping. It rests on two smaller diameter tubes that allow it to turn when you move the yellow knob. At the end of the large tube with the three mirrors is a cup with some coloured glass beads and other glistening bits and pieces. When you turn the kaleidoscope they tumble around in the cup and make beautiful patterns. The photo is just one example and not the very best, but still it looks interesting.
These pattern change with every little turn of the kaleidoscope. When you put another cup on the front with different bits and pieces the patterns and colours are different again. One can see an endless variations of reflections.
The kaleidoscope has three mirrors that run the length of the tube and therefore the images are reflected back and forth between the three mirrors and make these patterns. It looks like the whole tube is filled with colour and repeated patterns.