The following activities will introduce infrared radiation and its effects.
Step 1: Discovering Infrared
Introduce the task: List ways in which you can warm objects up. Elicit suggestions from the class. (List can include such methods as: placing an object over a fire or electric coils; using steam; using hot water; placing an object near a radiator; placing an object in the sun.)
Next, ask how each of the ways listed warm things up. (Fire, electric coils, steam, and hot water must be in contact with the object. Radiators are in contact with the air, which in turn heats an object. If students try to reason that the sun warms an object because it is hot, point out to them that the sun is neither in contact with the object nor is there air in space for the sun to heat.)
Ask, is there anything the sun has that comes in contact with us? (Sunlight)
Perhaps there is something about sunlight that heats objects up. To investigate this, we will need a tool to measure temperature and another tool to break light up into its parts. What tools do you think we would need? (Thermometer and prism.)
Tell your students that the first person to use the experiment they are about to perform was Sir Frederick William Herschel in 1800. Herschel was interested in finding the temperature of the colors of the visible spectrum. He discovered that temperature increased the closer he got to red. Herschel then placed a thermometer below the red spectrum and discovered an even warmer temperature. He called this part of the spectrum infra-red or 'below' the red. Students will discover infrared light by repeating Herschel's experiment. Teachers should consult the Herschel Experiment Web site (http://sirtf.caltech.edu/Education/Herschel/herschel.html) prior to conducting the experiment.
For the experiment to be completed, it must be done in sunlight. Outdoors on a sunny day is best. Break up the class into groups of 2 or 3. Distribute the boxes with prisms and thermometers. Also distribute journals and the Herschel Student Organizer for recording temperatures in the experiment.
First, students will record temperatures of three alcohol thermometers with blackened bulbs in the shade using their Herschel organizers. Next, using the box setups described in the preparation for teachers, they will pass sunlight through a prism and onto the three thermometers placed as follows: one in the blue region, the second in the yellow, the last just below the red. After five minutes, students will record the temperatures in their organizers.
After the experiment, have groups report their results. Did the thermometers have the same temperature? Which one had the highest temperature? (The thermometers should have different temperatures. The one with the highest temperature will be the one placed just below the red spectrum.)
Herschel did not have a name for the energy creating the higher temperature below the red spectrum. He simply called it infra (below) red. It is this part of the sunlight spectrum that heats the surface of the Earth. Although we can't see infrared light, we feel its effects because of the buildup and release of heat energy.
Have groups report their results to the Infrared Processing and Analysis Center of NASA at the California Institute of Technology. The email address is: firstname.lastname@example.org
The following activities will examine the nature of infrared light, how it fits into the electromagnetic spectrum, and applications of infrared light.
Step 1: How does Infrared Light Fit in the Electromagnetic Spectrum?
Now that we know infrared light is a part of sunlight, we need to ask what infrared is. To do this, we need to examine sunlight in greater detail.
At this time, it would be a good idea to make sure that your students know scientific notation, because light energy is measured in wavelengths. Stress that it's a good way to write large and small numbers. A decimal is placed between the first two significant digits and the skipped places counted. The count is negative for numbers less than one and positive for those larger than one. The final form is written with the significant digits multiplied by a power of ten. The power is the integer count of the skipped places.
Examples: 8,120,000,000,000,000 = 8.12 x 1015
.0000000000231 = 2.31 x 10-11
Break the class up into groups and distribute the "Catch Waves" Student Organizer. Have the groups go to the Space Telescope Science Institute Web site at (http://amazing-space.stsci.edu/light/CatchWaves_activation-frames.html) to examine sunlight in the Catch Waves lesson. Provide a FOCUS FOR MEDIA INTERACTION by telling them that they will now examine the nature of the electromagnetic spectrum and where infrared light fits in, answering the questions on their organizer as they complete the online activity. At the end of the lesson, groups should go to the "Beats Me - You Answer It" activity and answer questions #1, #2, #5, and #7 in their journals. When they are done, have groups report their responses. (Students will learn that the spectrum has a definite order set by wavelength or energy level. Infrared is one energy level of light with a particular range of wavelengths.)
With the knowledge that infrared light is a particular range of wavelengths in the electromagnetic spectrum, students will now examine the relationship between frequency and wavelength.
Take some time to review inverse proportions with the students. The main fact about inverse proportions is that as one increases, the other decreases. The general formula for inverse proportion is
y = k k is a constant
For our discussion, k will be the speed of light (c), y will be frequency, and x will be wavelength.
Break students up into groups again and have them go to the Space Telescope Science Institute site again at http://amazing-space.stsci.edu/light/makewaves-frames.html and complete the Make Waves lesson. Provide a FOCUS FOR MEDIA INTERACTION by asking them to write in their journals the effect frequency and wavelength have on each other. Include an example. (As frequency increases, wavelength decreases. This is an inverse relationship.) After completing the lesson, groups should go to the "Beats Me - You Answer It" activity and answer questions two and four in their journals. Groups will come together to report their findings and responses.
Step 2: How Would Images Photographed in Infrared Light Appear?
If we could see images in infrared light, what would they look like? In visible light, differences of color combine to give shape and meaning to what we see. Because infrared light causes the buildup and release of heat, differences in temperature serve the same purpose as color in visible light. Seeing in infrared would require the ability to see differences in temperature. Today we have special tools that allow us to do just that. To see temperature differences in visible light, we would use colors. For example, shades of blue and green would indicate colder temperatures; reds and yellows, the warmer temperatures. Sometimes the opposite is used; color choice is arbitrary in infrared equipment.
We will now investigate pictures in infrared. In this activity, students will discover that all objects emit infrared light unless they are at the same temperature as absolute zero. Also, they will see that the choice of colors used to show the warmest and coolest areas of an infrared picture is arbitrary. Distribute journals and student organizers for "Seeing Our World in a Different Light" to your students, and have them break up into groups. Tell them to go to the Infrared Processing and Analysis Center of NASA to view "Seeing Our World in a Different Light" at http://sirtf.caltech.edu/Education/IRapp/benefits.html. Provide a FOCUS FOR MEDIA INTERACTION by asking groups to review the pictures and text and answer the organizer questions as they complete the lesson. After completing the lesson, have groups report their findings and responses.
Step 3: How Can We Use Infrared Light to Help Us?
In this activity, students will realize that infrared light is useful in many different areas. By examining these areas, students will learn the practical side of infrared light.
Have students revisit the "Seeing Our World in a Different Light" Web page at http://sirtf.caltech.edu/Education/IRapp/benefits.html. At the bottom of the page are areas where infrared light is used in society. Assign each group two areas, except meteorology (we will use this section next as an ongoing activity). Provide a FOCUS FOR MEDIA INTERACTION by asking each group to visit the Web page linked to each assigned area and describe the beneficial uses of infrared in their journal. They should pay attention to the colors used to show hot and cold differences. Remind students to be accurate and detailed in their descriptions. When groups are done, have them report their findings.
This learning activity can culminate in a class display of the uses of infrared light. The author of the Web site says that students can download pictures; however, not all pictures are owned by them. If the owner is listed below a picture, have students obtain permission for downloading. This will be a good lesson for students in respecting copyright.
Students will study real-time infrared weather images and use their knowledge of infrared to predict the location and severity of thunderstorms.
Step 1: What is a Thunderstorm?
Ask students, "What weather effects do you associate with thunderstorms?" (List will include rain, wind, lightening, thunder, hail, dark clouds, cooler temperatures, and other items.)
"Do thunderstorms happen most often on hot days or cold days?" (Hot.) Obviously, infrared energy has an impact on making thunderstorms.
"Do more thunderstorms happen on humid days or dry days?" (Humid) Humidity is a good source of moisture for rain.
Ask students to recall times when they noticed moisture form from humid air. (Cold drinks, air-conditioners.) Cold helps moisture condense from humid air.
Reinforce these concepts: Thunderstorms happen more on hot humid days, and cold air helps water form from hot, humid air.
To get rain, we need to get the hot, humid air to an area of cold temperatures. Where would this be? (At higher altitudes.)
How does hot air get to the cold altitudes? (Hot air rises.) Hot air could also be given a boost upward by a cold air mass wedging underneath a warm air mass. Also, mountains can lift hot air as it flows over them.
Reinforce these concepts: Hot, humid air rises to cold altitudes that condense the moisture, forming rain.
What happens to the air when it is cooled? (It sinks back to the surface.)
The process of rising and falling air is called convection. This is responsible for the winds we feel in a thunderstorm.
If humid air is hot enough, it will rise to great heights. This will create severe thunderstorms. Many of these storms have heavy rainfall, damaging winds, and hail that can reach the size of baseballs or grapefruit. Sometimes the volume of rain will cause flash flooding. The energy of severe thunderstorms often produces dangerous cloud-to-ground lightening strikes. The U.S. National Weather Service will warn people when it finds severe thunderstorms. These storms are not to be taken lightly.
Step 2: How Can We Predict Severe Thunderstorms?
What could infrared light reveal about severe thunderstorms? (The temperature of clouds would indicate their height: the colder the cloud top, the higher the cloud. This would indicate the strength of the convection inside a thunderstorm and hence its severity.)
On a projection device, show the infrared picture taken by the GOES satellite of a severe thunderstorm. Distribute copies of the U.S. Weather Service warning for this storm. The warning is included with the Student Organizers. Have students examine the scale at the bottom of the picture to see what colors are being used to indicate cold and hot temperature differences. Temperatures are given in centigrade. Have a student read the U.S. Weather Service warning. Ask students to compare their descriptions of thunderstorms to the official notice.
Distribute journals and break students up into groups. Have them go to the Satellite data page of the National Center for Atmospheric Research-Research Application Program at http://www.rap.ucar.edu/weather/satellite to view real-time infrared images of North America. At the Web page, select infrared (color). You may also choose animation depending on the speed of your Internet connection. After making your choices, click Contiguous U.S. on the map. Provide a FOCUS FOR MEDIA INTERACTION by having groups list the temperature and location by state of the highest cloud tops of possible thunderstorms. Have them write this in their journals. Thunderstorms will look like cells. With practice, students will learn to distinguish the cloud tops of weather systems from individual thunderstorms. They should indicate if they think the thunderstorms are severe or not.
Sometimes thunderstorm cells have hooks around their edges. This could indicate the presence of tornadoes. On a projection device, show the GOES satellite infrared picture of tornado-producing thunderstorms. Point out the hooks. If they see hooks in their investigations, have students note them in their journals. When finished, have groups report their findings.
After reporting, have groups go to the Interactive Weather Network of the U.S. Weather Service at http://iwin.nws.noaa.gov/iwin/graphicsversion/bigmain.html. Ask them to click on the colored map of the U.S. This map shows current warnings and advisories by state. Provide a FOCUS FOR MEDIA INTERACTION by having them click on the state where they think severe weather is occurring according to their observations of the infrared cloud top map. When the state is displayed, have them click on Warnings and Advisories. They should write in their journals if any severe weather is noted. When finished, groups should report their results.
This can be an ongoing activity. Every day, one or a group of students will access the satellite and then the weather Web pages to note severe thunderstorms. After writing in their journal, the student or group reports to the class if severe weather is found.
Convert all the centigrade temperatures at the bottom of the satellite infrared color map to Fahrenheit and Kelvin.
Research Herschel's other notable discovery.
Imagine that you live in a world where you can see only infrared light. Write a postcard to your parents describing the beautiful sunrise you witnessed this morning.
A car that has just returned from a long trip is photographed in infrared light. Draw, using colors of your choice, what you think the picture would look like. Include a color key.
- Invite an architect to your classroom to discuss how infrared energy can be used to heat homes cheaply.
- Invite a representative from your town's emergency management division to discuss plans in the event of damaging thunderstorms.
- Invite a representative from your town or state building codes division to discuss how buildings can be made to withstand damaging thunderstorms.
- Invite a storm-chaser to show video clips of severe storms.