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Students should know the following (concepts for advanced physics classes are marked as such):
- Understand the different parts of the electromagnetic spectrum and how they differ.
- Understand the concept of a black body, how the sun and Earth can be represented as black bodies, and how these two black body spectra differ (advanced).
- Understand how temperature and wavelength are related (advanced).
- Understand the different ways by which materials may interact with electromagnetic energy (light).
- Understand the concept of absorption: molecules will absorb certain wavelengths of the spectrum while being transparent to others. Where absorption happens, the energy will be reemitted as thermal energy.
- Understand that the interactions of radiation with matter depends on wavelength and on the properties of the matter (molecules or particles).
- Understand what scattering is and where and why it happens.
- Understand that scattering varies based on wavelength, and that preferential scattering of shorter (blue) wavelengths by molecules in the atmosphere is what makes the sky blue. Scattering by larger particles (aerosols and cloud droplets) is less dependent on wavelength:
- These scatterings are known as Rayleigh and Mie scattering, respectively and are
represented by a probabilistic distribution of scattering direction (advanced).
- Understand how scattering of incoming radiation by aerosols and clouds affects the Earth’s climate.
- Understand how aerosol particles are formed, and the role they play in cloud formation.
- Longer wavelengths are more energetic.
- Light and heat are not related.
- The Earth reflects sunlight and that’s why the planet is warm.
- The definition of satellite (students will identify a radio telescope, which looks like a television satellite dish, as a “satellite”).
- CO2 molecules in the atmosphere primarily heat the Earth by absorbing energy from the sun.
- The ozone hole allows more heating of the atmosphere, causing global warming.
- Volcanoes cause global warming.
- Heat is a molecule.
- Energy is a molecule.
- The Earth’s atmosphere is made up primarily of oxygen and carbon dioxide.
- Laser beams get “thicker” with aerosol.
- “Smoke” and “cloud” are the same thing.
- No scattering is occurring when one can see the path of a laser beam (the opposite is true).
- “Aerosol” is something that comes out of a hairspray can.
- The sky is blue due to reflection off the ocean.
- Introduce the electromagnetic spectrum and the concept of electromagnetic energy. Students should understand that:
- Different parts of the EM spectrum have different wavelengths.
- Different wavelengths have different energies.
- The majority of energy emitted by the sun is of different (shorter) wavelengths than the
thermal energy emitted by the Earth (longwave).
- Introduce the concept of energy-matter interactions, and that absorption is one interaction that may occur in this case. Students should understand:
- How matter interacts with electromagnetic energy (light) by absorption and reemits this
energy as thermal energy.
- Molecules will absorb only certain wavelengths of the spectrum while being
transparent to others.
- Activity 1: The activity in this lesson will use jars and heat lamps to illustrate the
different absorption properties of different materials (white versus dark colors).
- Introduce the concept of atmospheric scattering. Students should understand:
- Rayleigh scattering occurs when light is scattered off many very small particles.
- Mie scattering occurs when light is scattered off of many larger particles.
- Activity 2: Students will explore the wavelength dependence of scattering. They will
observe how different colors of lasers will scatter in pure water and water
with extra particles added.
- Activity 3: Students will learn how atmospheric particles (aerosol) are created. Using
a UV pen, the instructor will create ozone gas, which, when combined with volatile
gases from an orange peel, will create particulates.
- Activity 4: Students will make a cloud in a bottle. A pressure change in a soda bottle
combined with particulates from smoke will induce liquid water to become a cloud.
- Some of the activities require materials. These are described in the activity description file. Supplementary in-class handouts for use during the activities are also provided.
- As described in the above document, it is beneficial, although not necessary, to have different-colored laser pointers in the activities of Lesson 3, particularly in the first activity. In the initial teaching, red, green, and blue (405nm) lasers were used; the difference between red and blue lasers was most illustrative. For a full list of materials needed for each activity, please see the accompanying pdf.
- This lesson was taught in a high school physics classroom, from regular physics (primarily ninth-graders) through AP Physics (grades 10-12). The lesson should be downscaled for regular physics according to the students’ prior knowledge.
- The lesson was taught in 2 block periods, with Lessons 1 and 2 on the first day, and Lesson 3 on the second day.
- The lessons should be taught in chronological order. It is beneficial for the students to have had prior exposure to geometric optics.
- This lesson comes with two handouts associated with the in-class activities. The handouts include pre- and post-activity questions evaluating students’ conceptual knowledge. It is useful to discuss these questions in class.
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- Physics 3c: Students know the internal energy of an object includes the energy of random motion of the object’s atoms and molecules, often referred to as thermal energy. The greater the temperature of the object, the greater the energy of motion of the atoms and molecules that make up the object.
- Physics 4e: Students know radio waves, light, and X-rays are different wavelength bands in the spectrum of electromagnetic waves whose speed in a vacuum is approximately 3 × 108 m/s (186,000 miles/second).
- Earth Science 4: Energy enters the Earth system primarily as solar radiation and eventually escapes as heat.
- Earth Science 8: Students know the thermal structure and chemical composition of the atmosphere.
- Investigation and Experimentation Standards: Students should develop their own questions and perform investigations.
- IV.A.2.b: Students should understand the inverse-square law, so they can calculate the intensity of waves at a given distance from a source of specified power and compare the intensities at different distances from the source.
- IV.B.2.b: Know the names associated with electromagnetic radiation and be able to arrange in order of increasing wavelength the following: visible light of various colors, ultraviolet light, infrared light, radio waves, x-rays, and gamma rays.
- L.2: Observe and measure real phenomena: Students should be able to make relevant observations, and be able to take measurements with a variety of instruments (cannot be assessed via paper-and-pencil examinations).
- L.3: Analyze data: Students should understand how to analyze data, so they can:
- a) Display data in graphical or tabular form.
- b) Fit lines and curves to data points in graphs.
- L.5: Communicate results: Students should understand how to summarize and communicate results, so they can:
- a) Draw inferences and conclusions from experimental data.
- b) Suggest ways to improve experiment.
- c) Propose questions for further study.
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Aerosol Plume over India
(NASA MODIS)
Atmospheric Scattering (Nic Beres)
Basics of Rayleigh Scattering
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- Grade Level: 10-12
- Time Frame: 1 week (2 block periods, with Lessons 1 and 2 on the first day, and Lesson 3 on the second day)
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SIO Entrance
Scripps Pier
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Design EarthRef.org
Sponsored by NSF and NSDL
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