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Download the worksheet (Appendix 1): .doc or .pdf
Specific Lesson Objective/Purposes:
The objective of this lesson is to illustrate the concepts of solar energy and the electromagnetic spectrum, and the function of the ozone layer in an inquiry based lesson for students in grades 7 through 12.
Materials Needed:
Globe, infrared thermometer, clip-on work lamp, “GE Reveal” halogen lamp, acetate sheet
Time Required:
Two or three class periods.
Procedures:
Solar energy, the electromagnetic spectrum and the function of the ozone layer are concepts perhaps intangible to students due to the scale of the systems, and the seamless developmental integration of light into human perception. In this activity, we hope to illustrate the energy of light using an infrared thermometer and a model of the Sun, Earth and ozone layer, and demonstrate the functional role of the ozone layer in protecting Earth from some of the radiation emitted by the Sun. Students are encouraged to develop and test hypotheses related to the model, increasing or depleting the effectiveness of the ozone layer by adding or removing material between the model Sun and Earth, and make observations about how the modifications enact changes in the temperature at the model Earth’s surface.
To introduce the procedures, the students first make observations at set time intervals about the temperature of the light, the globe and the air between the globe and light (Appendix 1). Students are then asked questions reflecting on the processes they observed, reinforcing that energy traveled from the light to the globe without showing a measurable change in the air temperature between the light and globe.
This introduction also acquaints students with the use of the infrared thermometer, and helps to reinforce its limits for measurement (in space, at surfaces), and where they may cause error in the experiment. For example, error may be caused by having a classmate standing “behind” the air in which they’re attempting to measure, or by measuring the temperature of a surface at an oblique angle. If students have made mistakes during this portion, the illustration can simply be reset by turning the globe.
The students then initiate the basic experiment by running the simulation again, this time with the acetate sheet placed half way between the light and the globe. Students are asked to make observations about temperature at timed intervals again, this time including the temperature of the acetate sheet.
If the experiment is run correctly, the acetate sheet will heat up, but the globe will heat up a much slower rate than it did without the sheet. Students are then asked questions reflecting on the processes they observed, reinforcing that energy traveled from the light to the globe, but was absorbed by the “clear” acetate sheet.
Students are then asked to form their own hypothesis about modifications to the model “ozone layer” and test these hypotheses. Example modifications may include doubling or tripling the acetate sheets, cutting a hole in the middle of the acetate sheet, drawing lines on the acetate sheet with erasable marker, or adding a sheet of construction paper, white or with dark color.
Evaluation of this lesson may be done using the answers to the questions provided in the appendix or by a test question that requests expected outcomes should a modification not tested by the students be made.
Closure to this lesson will be a recap of the observations made by the various groups with their modifications, hypotheses and outcomes. This lesson provides a segue way into climate and global warming, as the acetate may also represent the atmosphere in general.
Reflection:
This lesson worked well in its intended purpose to illustrate solar energy and the function of the ozone layer. To make this lesson more effective, in the future, we propose to provide a more structured initial experiment, perhaps going through that step as a class. The students were prone to aim the thermometers at oblique angles, thus getting an improper reading. The students were also prone to have classmates wander in behind the “air”, thus obtaining measurements of the temperature of the surface of their classmates, as opposed to the air they were attempting to measure.