Absorption and Reflection of Solar Energy
Participants will have the opportunity to use infrared temperature guns to measure the temperatures of multiple outdoor surfaces. Small groups will discuss their data in the context of albedo, heat capacity, absorption and re-radiation. Participants, will share ideas about how the activity may be incorporated into lessons on the greenhouse effect, solar radiation, weather, climate, Wien's Law, the Stefan-Boltzmann Law, and topics addressed in geoscience and climate change lessons.
As part of an overall lesson on Earth's energy budget, the objective of this inquiry activity is for students to describe how surface material type and color affect absorption and reflection of solar energy. Students collect data on the temperature of multiple outdoor surfaces using infrared temperature guns. The collected data provide a basis for inquiry into why the varied surfaces exhibit different temperatures. Students subsequently engage with concepts including albedo, heat capacity, absorption and re-radiation to explain the observed temperature differences. Understanding these concepts is a precursor to lessons addressing the greenhouse effect, solar radiation (ultraviolet, infrared, visible wavelengths), weather and climate, Wien's Law, the Stefan-Boltzmann Law, and topics addressed in geoscience and climate change lessons.
My students are elementary education majors in an introductory earth science course that focuses on the atmosphere. With little background about the nature of electromagnetic radiation, the complexities of how solar energy interacts with the Earth and the intricacies of the energy budget are difficult concepts to grasp. This activity first causes students to recognize that varied Earth surfaces have different temperatures and then compels them to understand why. It is important to establish this background before learning about weather and climate processes.
Why It Works
A highlight of the activity is that it uses natural sunlight and outdoor materials to examine differences in absorption and reflection. (Using infrared temperature guns can also extend to a discussion of wavelengths and energy.) Common classroom activities that often use indoor lights do not truly model solar and surface radiation, can provide inaccurate representations, and sometimes work poorly. In this activity, because students make observations in the natural environment rather than a lab, the connection to actual Earth processes is strong.