by: Gordon Gore

INVESTIGATION #1

You Need

2 small, flat plastic mirrors, with suitable vertical supports, 1 piece of plain white paper, letter size

What to Do

1. Hold the mirror vertically. Look into the mirror. Touch your right ear. Watch what the good-looking person in the mirror does. Which ear does he or she seem to touch?

2. Write your first name on a piece of paper. Look at your writing in the mirror. What is ‘unusual’ about what you see? Write your name so that it looks ‘right’ in the mirror.

3. Notice how AMBULANCE is written.  Why is it always written this way on the front of the emergency vehicle?

4.  Try writing AMBULANCE on a piece of paper, so that it looks normal in a mirror.

5. Prepare 3 file cards with words like the ones in the photographs #1, #2, and #3 below.

1.2.3.

6.   Hold card #1 in front of the mirror, as in the photograph. Why is one of the words ‘backward’, in the mirror, while the other two words are not?

7.   Hold card #2 in front of the mirror.  What do you see in the mirror?

8.   See if you can find a way, using a second mirror, to make card #3 reflect so that it is ‘not backward’.

Challenge!

Write similar words on a clear sheet of plastic. Hold the plastic so that you read the words, as they should appear. Does the mirror make the image appear ‘backward’, or is there some other reason?

INVESTIGATION #2

When you look in a mirror, where is the image? Is it on the mirror, in front of the mirror, or behind the mirror?

You Need: 1 plane mirror with a support, 2 pencils, 1 piece of blank paper, 1 centimeter ruler

Mark the reflecting surface of the mirror with a pencil line. (See photo)

1. Hold a pencil about 10 cm in front of a flat mirror, as in the photograph. (Hold the pencil in a vertical position when you do the experiment.) Look into the mirror and you will see an image of the pencil.

2. How far is this image from the rear of the mirror?  To find out, move a second pencil around behind the mirror until it appears to be in the same place as the image.

3. Push down on both the original pencil and the image-locating pencil so that a small mark is left on the paper on your desk.

4. Use a centimeter ruler to measure these distances:  (a) From the first pencil to the mirror surface and  (b) From the mirror surface to the image.

5. Try using other distances from the first pencil to the mirror surface.

Questions:

1. How do the two distances compare with each other?

2. Imagine you wish to photograph your image in a mirror. If you are 1 meter in front of the mirror, should you focus your camera at a distance of 1 meter or 2 meters?

3. Imagine that you run toward a mirror at a speed of 10 meters/second.  How fast will your image in the mirror approach you?

Is an image in a plane mirror really ‘backward’ (laterally inverted?)

Top: The word on the clear plastic sheet is ‘BACKWARD’. If you turn the sheet so the writing is toward the mirror, as you might do if you wrote it on a sheet of paper. The image certainly reads ‘backward’ (laterally inverted).

Bottom: If you hold the clear plastic sheet with the words ’NOT BACKWARD’ written on the side facing you, the image says ‘NOT BACKWARD’. It all depends on your perspective.

For a new twist on the same idea, check out the Sulfur Dioxide Puzzle available at Educational Innovations. Why would the cylindrical lens reverse the red colored word and not the blue one? What is different? Can you test your hypothesis? Great critical thinking question for students of all ages! This is perfect for a science table, display case or even the teacher’s desk! Lesson ideas are included!

The BIG Little Science Centre was started in February 2000 by Gordon R. Gore, a retired science teacher who has dedicated his life to teaching science in an interactive environment. The Centre currently operates out of four classrooms leased from School District 73 at Bert Edwards Science and Technology School, 711 Windsor Avenue Kamloops BC, Canada.