Lesson Plan #:AELP-PHY0020

## Laws of Reflection

AUTHOR: Douglas Vulcan, Florence Carlton Jr. High; Florence, MT

OVERVIEW: Teaching Laws of reflection to Jr High students presented a problem to me until I started to use this activity. Students develop the Laws of Refection by use of their own experimentation and observation. I give them as little help as possible making them come up with something that will work. The student must write in report form what ever procedure and conclusions that come from the activity.

PURPOSE: To develop the basic Laws of Reflection by observation of images of objects in plane mirrors.

RESOURCES/MATERIALS: 20 cm by 30 cm piece of card board ( to stick pins into), dissecting pins, small plane mirrors, clay (for mirror supports), protractors, rulers, and clear sheets of paper.

ACTIVITIES AND PROCEDURES: I let the students develop their own experiments. (These are suggested steps to follow)

1. draw a line across the center of a sheet of paper this becomes the reflective line in the experiment.
2. place this sheet of paper on the piece of cardboard.
3. place the mirror upright along the line on the paper support with clay or other type of mirror support
4. place two dissecting pins in front of the mirror. One of the pins becomes the object the other the observer pin.
5. while observing the image of the first pin rotate the card board so that the image and the second pin are in line with each other.
6. make marks on the paper along the line of sight between the two. "image and observer"
7. remove the paper from the card board, mark the lines of sight with a ruler, and measure the angles formed.
8. repeat the experiment placing the pins in new location
9. compare the angles in each trial.
TYING IT ALL TOGETHER: This one experiment can start one off on a whole series of experiments about plane mirrors. I usually ask the students to come up with a statement about how far behind the mirror is the image.

May 1994

These lesson plans are the result of the work of the teachers who have attended the Columbia Education Center's Summer Workshop. CEC is a consortium of teacher from 14 western states dedicated to improving the quality of education in the rural, western, United States, and particularly the quality of math and science Education. CEC uses Big Sky Telegraph as the hub of their telecommunications network that allows the participating teachers to stay in contact with their trainers and peers that they have met at the Workshops.

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