Day 1
- New groups
- Setup week 6 notes
- Mid-trimester is this Friday -- please do retakes if you want grades to improve. Full grades will be available on Moodle by the end of the day Tuesday
- Return quiz2 from Friday
The Penny Climate Model
We're going to simulate the climate using pennies!
Debrief, for your discussion and to put in your notes:
- Draw a picture showing the main components of the penny climate model.
- What is the main source of energy for the earth to stay warm?
- Define albedo
- Describe the goldilocks phenomena that causes the earth to have a stable temperature
- What would the average temperature of the earth be like if we had no atmosphere? What is the average temperature with an atmosphere?
- Why when we build models of the climate system (or any other complicated system) would we start with the simplest model we can?
- What role does comparing data with model output have in improving a model? Give an example from the penny climate model.
- What complications have been ignored in the simple climate model?
- What did the Futurama climate model get right/wrong?
Day 2
- Temperature pair examples
- Seasons and the Sun
- Some details about radiation
Day 3
Blackbody radiation simulation
“Blackbody” is a term used to describe the electromagnetic waves (think light) given off by an object. Of course in order for such an object to emit electromagnetic waves, it must get hot. In this lab you are going to observe the nature of electromagnetic waves given off by objects of different temperatures and determine if there is an empirical relationship between an object’s temperature and the waves emitted.
You will be using a simulation of the electromagnetic radiation given off by objects of different temperatures, all the way from the earth to our sun. Both the peak frequency of the radiation given off and the intensity of radiation vary with the temperature of the object.
Go to http://phet.colorado.edu/en/simulation/blackbody-spectrum and run the simulation.
Part I Blackbody spectrum of an incandescent light bulb.
Set the temperature of the blackbody to 3000 K. This is approximately the temperature of the tungsten filament in an incandescent light bulb which is a good black body. Use the zoom tools so that you can observe a large peak (3.16 on the vertical axis and 3 on the horizontal axis would be good). Be clear about the information on each axis. Intensity is the amount of light given off and the wavelength of the waves is given on the horizontal axis.
- Based on the graph, does the light bulb produce visible light? How can you tell?
- Does the light bulb produce X-rays (wavelength around 1 nm or nanometer)? How can you tell? (Hint: does the graph ever truly go to zero?)
- Based on the shape of the graph would you expect the light bulb to emit radio waves? Would the amount be significant? Explain.
- For the light bulb, which wavelength will be brightest? Is the peak at visible light wavelengths?
Click Save. (The curve will turn yellow)
Part II Comparing spectra of different objects.
Set the temperature to 615 K, this is comparable to the temperature in a very hot oven. Notice that the RED line is the radiation emitted by the oven. The line should appear flat, but it isn’t. Zoom the y axis in to read .001 and zoom the x-axis out.
- How is the curve produced by the oven similar to the curve produced by the light bulb?
- How is the curve produced by the oven different from the curve produced by the light bulb?
- For the oven, which wavelength will be brightest? How does this wavelength compare with the wavelength of greatest intensity for the light bulb?
Set the temperature to 5600K. This is approximately the surface temperature of the sun. You’ll need to zoom in on the horizontal axis and zoom out on the vertical axis.
- Compare the most intense wavelength produced by the light bulb to the most intense produced by the sun.
- Explain the relationship you see between the peak in radiation emitted by the sun and where that peak lies in the visible spectrum.
- Is there evidence of the sun producing harmful ultraviolet radiation? Explain.
Part III, Graphing
Vary the temperature from 200 Kelvin to 6200 Kelvin in increments of 500K. Make a table in Excel of temperature, wavelength of the peak in spectra, and maximum intensity. Convert temperature to degrees centigrade and also to Fahrenheit. Graph temperature (in centigrade) vs spectral peak in Excel. Also graph temperature vs maximum intensity in Excel. On the graphs indicate the average temperature of the earth. On the spectral peak plot indicate the range of visible light. Also indicate where on the curve you would find Earth and the Sun.
- How does the intensity of the emitted radiation vary with temperature?
- How does the wavelength of the peak vary with temperature?
- Compare the plot of temperature vs intensity made for here with the graph of temperature vs intensity for the set of light bulbs at the beginning of this worksheet.
- As the Earth warms up, what will happen to the amount of longwave radiation it emits?
- Will this change in emitted radiation tend to warm or cool the planet? Explain your answer.
Day 4
Quiz on electromagnetic radiation and temperature. Requiz on climate pairs.
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