Investigating Energy from the Sun (Developed by SEPUP)

1. Introducing Sunlight

Students read about a fictitious student who is concerned because his great aunt has cataracts. They learn that cataracts are related to sunlight, specially ultraviolet (UV) rays, and that all ethnic groups, and even animals, are at risk. The discussion of this health issue introduces the need for an investigation of sunlight. Students' current knowledge and preconceptions of light and its associated energy are assessed, and students are presented with current scientific models of light.

2. Investigating Visible Light

Students begin their exploration of light by investigating the colors of the visible spectrum. Students first observe how a prism splits white light into its component colors. They then investigate the energy levels of the different colors of white light through use of a phosphorescent material. To help explain the observation that a prism separates light into a spectrum of colors and the observation that colors at the blue end of the spectrum have higher energy levels than those at the red end, students are introduced to the concepts of frequency and wave length.

3. Transmission, Absorption, and Reflection

Students learn more about the properties and different types of light by investigating transmission, absorption, and reflection. Students investigate how four thin films, each made of a different material, selectively transmit light and heat. The quantitatively compare the amount of heat transmitted and quantitatively compare the amount of visible light transmitted. Finally, students decide which film they would choose to purchase for their for their car windows. In Thinking More About Investigation 3, "Comparing Sunglasses," Students analyze transmission graphs or sunglass lenses.

4. Properties of Infrared Energy

Students learn about energies emitted from the sun and, in particular, the properties of infrared energy. Students refer to their knowledge of frequency, wavelength, and energy levels to learn about the discovery and applications of infrared energy and other energies that are fundamentally electromagnetic in nature.

5. Selective Transmission of Ultraviolet Energy

Students detect ultraviolet (UV) energy transmission by performing a similar investigation to that of Investigation 3, "Keeping Cool." They test four films to determine which film selectively transmits ultraviolet energy. In Thinking More About Investigation 5, "Blocking the Sun," students investigate the effect of sun block lotion on ultraviolet transmission and relate it to human health effects.

6. Increased Ultraviolet Exposure

Students explore the concept of increased risk by investigating health risks due to sunlight that is reflected onto the skin from sand, snow, or water. Then they consider the benefits and trade-offs of activities that involve increased ultraviolet exposure.

7. Personal Protection Plan

Students analyze a series of fictitious biographical case studies to determine the relative risk of cataracts and skin cancer for each person described. Each biography contains information about the person's geographic location, childhood UV exposure, skin color, and personal and family history of symptoms. After analyzing the fictitious biographies, each students determines his or her own relative risk of cataracts and skin cancer, and then creates a personal protection plan to help reduce UV exposure risk.