# Step-by-Step

In this Section

## Part 1: Electromagnetic spectrum

1. Click on this link.
2. Click on the wavelength scale.
3. Students can list all the names of the wavelength spectrum listed below the scale with the approximate wavelength range for each of them.  Note that it would be better to use nm or μm as the unit of wavelength (it is expected that students will be able to convert to these units from meters).
4. Note some examples related to the different spectrum ranges.

## Part 2: Blackbody radiation

1. Open the blackbody radiation applet
2. Select a temperature by moving the slider
3. Click on the x- and y-axis zoom in and zoom out buttons until the blackbody emission spectrum becomes visible.  Typical choices:  Sun: x-axis: 0 to 3 and y-axis: 0 to 100;  Earth: x-axis: 0 to 48 and y-axis: 0 to 0.0001
4. Note the wavelength location of the maxima of the radiation spectrum curve.
5. Change the temperature and repeat steps 3 and 4.
6. Complete the discussion questions on the student summary sheet

## Part 3a: Greenhouse gas interactions with EM radiation (middle school students)

1. Open the greenhouse gas and light applet
2. Select a molecule.
3. Choose and EM radiation spectrum
4. Move the slider on the lamp to start the flow of particles with energy corresponding to the chosen spectrum.
5. Note if the molecule interacts with the selected spectrum.  An interaction is characterized by the excitation of the molecule because of the absorption of the incident energy.  As the molecule returns to its original state, it re-emits radiation.  Notice that the radiation is emitted out in all directions.
6. Choose a different EM radiation spectrum
7. Repeat steps 4 and 5.
8. Repeat steps 4-7 with all the different molecules.
9. Fill out the table indentifying the interactions between the different molecules and EM radiation spectrum ranges.
10. Complete the discussion questions on the student summary sheet.

## Part 3b: Greenhouse gas interaction with EM radiation (high school students)

1. Open the greenhouse gas applet link
2. Click on the picture under “Collisional Heating by CO2 in the Atmosphere”.

3. Select a gas species.

4. Click on Start.
5. The window will now display the infrared (IR) absorption spectrum of the selected molecule.  Note that the molecule only absorbs in selected wavelengths in the IR range.
6. In the bottom of the screen, click on IR spectrum, Black body curve, and wavelength (nm).
7. Waves/particles with energies corresponding to the selected wavelength will pass near or through the selected molecule.  If the wavelength of the EM radiation corresponds to the absorption spectrum of the molecule, then the molecule may absorb the energy, get excited, and re-radiate the energy or lose the energy by interaction with the atmosphere (clink on the “Atmosphere” button in the bottom of the screen to visualize the collisional interaction between the excited molecule and the other molecules in the atmosphere.
8. Note the absorption wavelength of the selected molecule corresponding to the EM emission spectrum of the Earth (Black body curve on the screen).
9. Repeat for different selections of gas molecules.
10. Complete the discussion questions on the student summary sheet.

## Part 4: Greenhouse effect

1. Open the greenhouse effect applet
2. Set the greenhouse gas concentration to "none"
3. Note the temperature on the thermometer.
4. Increase the greenhouse gas concentrations to 1750 (pre-industrial) levels.
5. Note the temperature on the thermometer.
6. Observe the motion of the Sunlight and infrared photons.  Note that infrared photons can be seen to be headed up from Earth’s surface (blackbody emission) as well as headed down towards Earth’s surface (greenhouse effect).
7. Increase the greenhouse gas concentrations to other values (ice age and high) and note down the connection between greenhouse gas concentrations and temperatures.
8. Complete the discussion questions on the student summary worksheet.