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AST 151A Lab: Greenhouse Gases
Note: This lab is adapted with permission from Northern State University and PhET.
This simulation will open in your browser (Firefox recommended).
Greenhouse gases are those gases in our atmosphere that reflect certain kinds of light
back down, instead of allowing the excess light to escape into space. Up to a point, the
greenhouse effect is a good thing. It keeps the surface temperature of our planet
comfortable for human habitation. However, it’s possible for the effect to become to
strong and raise the average temperature far enough to cause problems. That is part of
what we are experiencing now in global warming and its corollary effects.
In this lab activity, you will use a PhET simulation to investigate how different
frequencies of light interact with different gas molecules. Based on the data you collect
and information you can look up, you will then answer several questions.
The frequencies of light are microwave, infrared, visible, and ultraviolet.
The gases are nitrogen, oxygen, carbon dioxide, water vapor, and ozone. (Carbon
monoxide and nitrogen dioxide are excluded from this exercise.)
Procedure
Step 1. Open the sim found at https://phet.colorado.edu/sims/html/molecules-andlight/latest/molecules-and-light_en.html . (This will open in your browser.)
Step 2. Spend a couple of minutes learning how the sim works. The “flashlight” has a
slide switch. You can select items on the bottom and right menus. The pause and set
buttons in the lower right allow you to watch something in slow motion.
Step 3. When you are ready, begin your exploration. Try each combination of light
frequency and gas (shown in the table below) for about a minute. Does the gas act like
a greenhouse gas for that frequency of light? The answer is YES if more than 10% of
the photons are scattered by the gas. Otherwise, the answer is obviously NO. (It will
be pretty clear to you. There are no “close calls” in this simulation!)
When you are done, you will have a table full of YES and NO entries. You may then
proceed to the questions. Your data and answers to the questions will be recorded in
your lab report. Upon completion, upload your lab report to Blackboard.
Questions may require you to look up some information online (or in your textbook).
You may also refer to the light spectrum included in the simulation.
Microwave
Infrared
Visible
Ultraviolet
Nitrogen
(N2)
Oxygen
(O2)
Carbon Dioxide
(CO2)
Water Vapor
(H2O)
Ozone
(O3)
Q1. Which frequency of light in the table above carried the least energy? The most
energy?
Q2. Greenhouse gases will scatter more than 10% of the incident photons. Which
gases investigated in this sim caused that effect?
Q3. Greenhouse gases do not scatter different wavelengths uniformly. Which
wavelength investigated in this sim was scattered the most? Next most?
Q4. Did the scattered photons simply bounce off the gas molecules in random
directions? Or, were they absorbed and remitted in random directions? [You can slow
down the “flashlight” and use the pause/step forward buttons to check this out. The sim
is pretty accurate!]
Q5. Which molecules were destroyed by any frequency of light? With which frequency
did this occur? What is the significance of this?
When submitting your lab report, be sure to use the file name convention for this
course: last name, first initial, lab number (e.g. “newtoni-lab06”).
Grading Rubric
Data table complete/correct
Questions (8 pts each)
File name correct format
Name and date included
Report submitted on time
Total
40%
40%
5%
5%
10%
100%
Name:
Date:
Lab 07 – Greenhouse Gases
Microwave
Infrared
Visible
Ultraviolet
Nitrogen
(N2)
Oxygen
(O2)
Carbon Dioxide
(CO2)
Water Vapor
(H2O)
Ozone
(O3)
Q1. Which frequency of light in the table above carried the least energy? The most
energy?
Answer:
Q2. Greenhouse gases will scatter more than 10% of the incident photons. Which
gases investigated in this sim caused that effect?
Answer:
Q3. Greenhouse gases do not scatter different wavelengths uniformly. Which
wavelength investigated in this sim was scattered the most? Next most?
Answer:
Q4. Did the scattered photons simply bounce off the gas molecules in random
directions? Or, were they absorbed and remitted in random directions?
Answer:
Q5. Which molecules were destroyed by any frequency of light? With which frequency
did this occur? What is the significance of this?
Answer:
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