Sunrise-Sunset Demo
| This simple demo will help students understand why the rising and setting Sun is reddish-orange in color. As a bonus, they may also observe a faint sky-blue color and realize why the sky is blue. I use the demo as we begin our study of the atmosphere because it seems that the concept of “wavelengths” comes up so often during the unit . . . For example, topics such as the greenhouse effect and the absorption of UV by ozone molecules both involve an understanding of wavelengths. Materials An overhead projector with screen, a 1-gallon jar, a small (1/8th tsp.) measuring spoon, a packet of non-dairy coffee creamer, a dark classroom, large spoon or ruler for stirring, flashlight (optional) Directions 1. Fill the jar with water to about 2 inches from the brim. 2. Place the jar onto the overhead projector (no lid). Darken the room. Turn the projector on, projecting the light through the jar of water onto the screen. 3. Have the students observe the “whiteness” of the light projected onto the screen. Remind them that “white light” includes wavelengths of ROYGBIV. Ask them “what is the difference between red light and blue light?”. Most of my freshmen know that the red light has a longer wavelength than blue light. Also, point out the “colorlessness” of the water in the jar. 4. Next, take 1/16th tsp. of the powdered creamer and stir it into the water. Have the students observe the color of light projected onto the screen and the appearance of the water. They may begin to see an orange tint on the screen and a very faint hint of blue in the jar of water. 5. Add another 1/16th tsp. of creamer to the jar of water, stir, and observe. By now the reddish-orange color on the screen should be obvious, and the very faint sky-blue may be apparent in the water, especially near the bottom of the jar. 6. Add another 1/16th tsp. of creamer, stir, and observe. If a flashlight is available, shut off the projector and then shine the flashlight horizontally through the water toward the eyes of the students so they can see the reddish setting or rising Sun. Explanation Light from the Sun includes wavelengths of red, orange, yellow, green, indigo, and violet (ROY G. BIV). The “white light” from the projector bulb also includes these colors (wavelengths). During the middle of a clear day, the shorter waves, especially blues are scattered by air molecules, dust, and pollutants, whereas the longer waves (ROYG and some of the longer blue wavelengths) are able to pass through the atmosphere. Apparently, air molecules are just the right size to "scatter" the shorter waves (especially blues). As a result, when we look at the atmosphere, we see the "scattered" blue light. When the sun is rising or setting, sunlight must pass through more atmosphere before reaching our eyes. Even more wavelengths, including the longer blues, the greens, and the yellows are scattered. As a result, when we look at a rising or setting Sun, we see only the reds and oranges, which haven’t been scattered, or "filtered out" by stuff in the atmosphere. The powdered creamer has the same effect on light from the bulb as the particles in the atmosphere have on sunlight. Source for the explanation: The Weather Book by Jack Williams/USA Today, 1992, published by Vintage Books (a division of Randon House) |
Worksheet 11-2: Lunar Phases and
Earth, Moon, Sun Relationships
Modified from Glenn F. Embree
Instructions:
Using the data you collected, the diagram on p 604 of Tarbuck and Lutgens, and information from the demonstration described below, answer Questions 1 through 16.
Use a styrofoam ball, spotlight, and chair to simulate phases of the Moon. Sit on the rotating chair, which represents the earth. Turning the chair to the left duplicates the earth’s rotation on its axis as observed from above the North Pole. Holding the ball by the stick at arms length while rotating the chair demonstrates the revolution of the Moon around the earth. The spotlight represents light from the Sun.
a. Observe how your perspective of the lit- and shadowed-side of the “Moon” (ball)
changes as it moves around the “earth” (you).
b. Observe the relative positions of the Moon (ball), Sun (light) and earth (you) during different phases of the Moon.
c. Turn the chair while demonstrating each lunar phase to visualize sunrise and set as well as moonrise and set.
d. We always see the same side of the Moon from earth. Use the X on the ball to designate the near side of the Moon. Experiment with the ball to demonstrate how it is possible to always see the side with the X while the ball (Moon) revolves around the chair (Earth).
Questions:
1. Where in the sky is the full-Moon at sunset?
2. At what time of the day/night is the first quarter Moon directly overhead?
3. Where in the sky is the third quarter Moon at sunset?
4. Why don’t we see the Moon during the new part of the phase?
8. What time of the lunar day would it be?
9. If you were on the Moon looking at the earth during full Moon, what would you see? (i.e. How would the Earth appear to you?)
10. If you were on the Moon looking at the earth during a new Moon, what would you see? (i.e. How would the Earth appear to you?
11. What produces a lunar eclipse? Duplicate these conditions with the ball, light and chair.
12. What is the difference in appearance between a new moon and a lunar eclipse?
13. During which phase of the moon does a lunar eclipse occur?
14. What produces a solar eclipse? Duplicate these conditions with the ball, light and chair.
15. During which phase of the Moon does a solar eclipse occur?
19. Why don’t we have a lunar or solar eclipse every month?
16. Explain how the Moon’s rotation and revolution interact to make it possible for us to always see one side of the Moon and never the other.
Laboratory 11: Lunar Observations
Modified from Glenn F. Embree
Introduction
The purpose of this lab is two-fold: 1) to help you better understand the relationship between the earth, the Moon, and the Sun and 2) to give you an opportunity to apply the scientific method to personal observations. The Moon is a beautiful object that we all enjoy. It provides light for us on some evenings but not others – why? It sometimes appears during the night and at other times is present during the day. Is there a pattern? The Moon seems to grow from a sliver to a fully-lit disc and then shrinks back to a sliver? What is causing this effect? Ultimately, you should be able to predict the Moon’s movement throughout its cycle of approximately one month.
Instructions (Please read carefully):
Work for this lab will begin with the first new Moon of the semester and will require daily observations for four weeks. During the first lab of the semester, methods and procedures will be demonstrated. It will then be your responsibility to carry them out. If you don’t understand one or more of the procedures, ask questions in lab before the new Moon occurs. The date and time of the New Moon will be provided. Each day you will record the following information in the table provided on Worksheet 15-1: date, time, phase, altitude, azimuth degrees from north, and the Sun/Moon angle. You will provide a simple drawing of the lunar phase.
It will be discovered that you cannot make your observations at the same time each day. Each week, you should choose a time to make the observations for that week; then, adjust your time for the following week. To help determine a good time to make your observations, you can check http://aa.usno.navy.mil/ for the time of moonrise and moonset for any place on a particular day.
Lunar phases are shown in Figure 21-23 of your text book.
The altitude above the horizon can be approximately determined by using either of the following methods: 1) a clenched fist held at arms length, which represents about 10° or 2) the clinometer provided in the lab.
The azimuth is the angle in degrees measured clockwise from due north (0°). The other cardinal directions are 90° for east, 180° for south, and 270° for west. Again, a clenched fist held out at arms length is about 10°. You may also use the “compass” provided in the lab.
The Sun/Moon angle is measured in the same manner as azimuth but is the number of degrees between the two bodies. If the Sun has set or has not yet risen, you can estimate the angle by determining the time of sunset or sunrise. The Sun appears to move about 15°/hour as the earth rotates; therefore, if using sunset, measure the angle between the Moon and the western horizon and add 15° for each hour since the sun has set. If using sunrise, measure the angle between the Moon and the eastern horizon and add 15° for each hour before the Sun is due to rise. Sunrise/sunset times are found on the web site listed above.
Do not look directly at the Sun while making these measurements.
Growing Alum Crystals in class or at home.
Alum crystals are beautiful and extremely easy and safe to grow. All it takes to grow these crystals is mixing alum with hot tap water and waiting a few hours. The alum is a kitchen spice used to make pickles crispy, so the project and the crystals are non-toxic, which makes it great for a class project or any project where safety is a concern.
Growing Alum Crystals
To grow alum crystals: ½ cup of boiling hot tap water plus 2-1/2 tablespoons of alum. Dissolve the alum in the water and allow the solution to sit undisturbed for a few hours. I used a pyrex measuring cup because it was easy to measure out the water and microwave it to boiling. When you take the water out of the microwave and put the alum in it, be aware that the alum will make the water bubble up the first time, so be careful not to get burned. Make sure the alum is dissolved. The water should be a milky white color. Boiling water is best, because it will make the alum crystals dissolve quicker and more efficiently.
What to Expect
After 30 minutes, you can see the crystals beginning to form. You can watch them grow larger and larger as time passes. You can expect to see a few large single crystals and some clumps of smaller crystals. When you are happy with the crystals, just take them out and examine them or display them. Some may artificially twin, these are particularly fragile and will often break into separate pieces when you take them out of the solution if you're not careful. Two hours gives you a decent size of crystal. Depending on your solution mix (whether or not you made more or less) the crystals will only grow to a point unless you pour more solution in. You may get bigger crystals as the previous ones may act as seeding crystals – something the others can grow on.
Clay Contour Lines
1. Build a small “mountain” of clay (or have your students build their own mountains)
2. Place “mountain” in a container (preferably with clear sides)
3. Mark the sides of the container with a standardized measurement representing elevation.
4. Fill container with water up to the first measurement.
5. Use a toothpick to trace around the top of the water line (this is your lowest contour line)
6. Continue following this procedure until you have traced the top contour.
7. Remove the water from the container.
8. Stand over the “mountain” and draw the contour lines on a piece of paper as you see them.
