Goal: Students learn that waves of energy bend when they pass through different substances, which allows scientists to measure traits of the atmosphere.
Specifically, students will learn that electromagnetic radiation, including light and radio waves, bends when it passes through substances with different densities. The amount of bending of radio waves beamed from one satellite to another allows scientists to measure traits of the atmosphere, such as temperature, pressure, and humidity, at different heights.
Engage students with a demonstration of bending light rays.
Begin the lesson with a physical demonstration of light bending as it passes between air and water to spark students' curiosity with a very tangible example.
Later in this lesson sequence students will use a computer-based simulation to explore details of the phenomenon of refraction. Before students encounter the computer simulation, it is important for them to observe refraction with their own eyes "in the real world." After seeing a physical demonstration, students wiil be more prone to accept the results of the computer-based simulations as being accurate models of physical events. Also, demonstrations of actual physical phenomena can be more memorable for many students than something viewed on a screen.
The Introduction: Physical Demonstration of Refraction section of our Measuring Density by Bending Light activity, provides three options.
Explore the relationship between density and bending light rays with a computer simulation.
Students explore refraction in more depth using a computer-based simulation. The simulation allows students to quickly switch between substances that light passes through, helping them discover how light refracts by different amounts depending on the index of refraction and density of the substance. Students will determine the relative density and index of refraction of three unknown samples by conducting "virtual experiments" within the computer simulation.
- Tell students to complete the second and third sections of the Measuring Density by Bending Light activity, Computer Simulation of Simple Refraction and Using Refraction to Determine Density.
- After completing their work with the computer simulation have students watch this short video that explains refraction and describes Snell's Law, the concept from physics that explains the mathematics of refraction. (Note: the full video is 7 minutes long and requires registration to view; however, the key points needed for this activity are contained in the first 2:20 of the video, which does not require registration to see.)
Explain how the bending of radio waves allows meteorologists to measure the atmosphere.
Students read about and compare two types of electromagnetic radiation, visible light and radio waves and about the layers of Earth's atmosphere. Finally, they view a video about the COSMIC satellites and radio occultation, and explain use the Electromagnetic Radiation & Atmosphere Layers worksheet to explain how the bending of radio waves beamed between satellites allows scientists to measure traits of the atmosphere.(See list of readings and video below.)
Students may need help with some of the steps in the logic of how the radio occultation technique provides scientists with data about temperature, pressure, and humidity at different heights in the atmosphere. Refer to our Radio Occultation web article that provides a more detailed explanation of the radio occultation technique and its use for measuring aspects of the atmosphere. That page also lists the sequence of concepts that you will need to guide your students through so they will understand radio occultation and how it is used to measure the atmosphere.
Student Readings and Video mentioned above:
- Density (closely related to index of refraction)
- About Electromagnetic (EM) Radiation: Compare Visible Light with Radio Waves
- About the Layers of Earth's Atmosphere
- COSMIC Video [ADD LINK ONCE VIDEO IS LIVE]
After reading about electromagnetic radiation, have students fill in the table on the Electromagnetic Radiation & Atmosphere Layers worksheet comparing red and blue light with radio waves. Ask them to make a prediction, based on a comparison between red and blue light, about how the bending of radio waves might compare with the bending of visible light. Red light has a longer wavelength than blue light, and red light bends less than blue light. Since radio waves have much, much longer wavelengths than visible light (either red or blue), it is reasonable to expect that radio waves bend less than rays of visible light of any color. The desired values that students should fill in on the table are shown on the worksheet answer key.
After reading about the layers of Earth's atmosphere, have students fill in the table comparing the lower layers of the atmosphere on the Electromagnetic Radiation & Atmosphere Layers worksheet. Desired student responses are shown on the worksheet answer key.
Elaborate by having students interpret data from COSMIC that shows atmosphere layers.
- Students will interpret a plot of temperature vs. altitude data that was generated by the COSMIC satellite using the radio occultation technique.
- Show students the graph below of temperature vs. altitude data. Tell them it was created from data from the COSMIC satellite using the radio occultation technique. Ask them to identify the altitude of the tropopause, the boundary between the troposphere and the stratosphere, and to explain their reasoning.
The tropopause is at an altitude of about 17 kilometers in this graph. Below 17 km, in the troposphere, temperatures decrease with altitude. Above 17 km, in the stratosphere, temperatures increase with altitude.
Evaluate students' ability to transfer knowledge of refraction to different situations.
Lead students in a discussion of situations in which it is useful to be able to infer the traits of some material or object from afar without directly touching it with any sort of measurement system. Examples include satellite remote sensing, use of infrared thermometers to measure the temperature of a lava flow, and the use of telescopes and spectrometers to study distant stars or planets.
Ask students to explain how the bending of light tells them something about the air in each of the following situations:
- when the Sun looks like a squished oval instead of a circle at sunset or sunrise
- when the pavement in the distance appears to shimmer and looks like a silvery puddle of water on a hot summer day
- when stars twinkle at night
See the Part 1 Rubric for examples of student answers at different levels of proficiency.