ALEX Lesson Plan

In this activity, students will model how the directness of sunlight affects the heating of Earth’s atmosphere at the equator. Students will demonstrate that Earth’s shape has a direct effect on the unequal heating of the atmosphere. The students will discover how the tilt of Earth’s axis affects the amount of sunlight that reaches different regions of the earth’s surface thus causing different seasons.

This lesson results from the ALEX Resource Gap Project.

Materials

• Masking tape (1 roll)
• Ruler (2 per student or group)
• Flashlight (not LED) – old-fashioned ones with C or D batteries work well (looking for heat to be produced) (1 per student or group)
• Graph paper (1 sheet per student or group)
• Thermometer (the bulb – colored with a Sharpie black or dark green +120 to -20 F) one per student or group)
• Clock/stopwatch/something to measure time (1 per student or group) timer on phone may be used
• Colored Pencils/markers (6 different colors per student or group)
• Copy of the laboratory procedures, charts, graphs, and questions. Solar Angles and the Unequal Heating of the Earth  (1 per group)

Technology is not required for this activity; however, a search engine could be utilized to access information pertaining to the activity.

Background Information:

     “The temperature of the Earth's atmosphere comes from the Sun's radiant energy warming the Earth's surface. The weather, climate, and seasons of a given area of the Earth depend on the temperature, which measures the atmospheric energy."

In this activity, you will model how the directness of sunlight affects the heating of the earth’s atmosphere (at the equator).  You will demonstrate that the earth’s shape has a direct effect on the unequal heating of the atmosphere. You will discover how the tilt of the earth’s axis affects the amount of sunlight that reaches different regions of the earth’s surface thus causing different seasons.”                                      

Explain: Background Information

The Background Information above links to Chapter 4: Angle of Light Rays and Surface Distribution: A Structured-Inquiry Activity

Page 19: Probing Further:  would be a good Formative Assessment Activity to gauge student awareness prior to the lesson.

Page 22: Background Information for Teacher is an excellent resource for information prior to planning lesson.

Prior to lab:

The teacher should set up each station or area with ~3 feet of masking tape, 2 rulers, 1 flashlight, 1 sheet of graph paper, 1 thermometer, stopwatch, and 6 different colors of pencils/markers/crayons.

Skills students should know:

Students should be able to correctly use a ruler, be able to read a thermometer, use a stopwatch, be able to correctly set up a graph (including creating scales for the x- and y-axis as well as all labels and title), plot a graph (line and bar), be able to use a search engine such as Google.

Knowledge the students should understand:

Students should have a basic understanding of seasons relationship to the 23.5^o tilt of the Earth’s axis, solar angles and solar radiation, a basic understanding of the Cosine Projection Effect. 

The picture (PICTURE  page 1) represents the solar angels at noon, 2 o’clock, and 4 o’clock. Notice the solar shadow on the paper is elongating. Use this information to explain the Cosine Projection Effect. (Cosine Projection Effect:

When you tilt a surface away from a beam of light, you spread the same density of light across a larger area.) Also use this information to explain the mathematical relationship (inverse) of the sun’s angle (surface sunlight) to intensity and distribution.

• Oblique (obtuse/acute) angles: less light (less solar energy– heat); greater surface area
• Right angles: more light (more solar energy– heat); less surface area

This lab is designed to be performed before a detailed explanation is provided to students. The gathering of the data, as well as graphing of the data, is key prior to teacher explanation.  After graphing has occurred (teacher may have to assist in scaling) on all 3 graphs, then the teaching moment can occur.  It is recommended that the teacher perform the lab in advance. This will allow the teacher to gather a data set that can be graphed in advance to use as the teaching template. NOTE: not all students will get the optimal data sets so having one ready to display on smart board or projector is easier than trying to find student ones that meet the criteria.

What should be seen: line graphs will vary but there should be an increase or constant line over time. With the perpendicular increasing, the most (90^o angle) and the horizontal increasing the least (180^o angle) and the 6in above table (~45^o angle) being in the middle.  The curvature should be similar to the perpendicular with their choice being in between. The bar graph of the temperature should be similar in height. This graph shows the perpendicular the highest with the horizontal being the lowest.  The perpendicular temperature represents summer with the 6in being fall/spring and the horizontal representing winter. Fall/Spring being similar in average temperature range can be shown as the same graph plot. You can also use this to represent times of day with 90^o being noon and 6in above table being ~ 4 PM and 180^o being dusk. Explain to students that the solar radiation decreases as the solar angle decreases. The third graph is the illuminated boxes vs angle.  This should show the angle increases as the number of boxes illuminated increases. Explain that this means that as the solar angle increases the surface illumination increases.  Together these two data sets show the Cosine Projection Effect as solar radiation increases the surface are affected decreases and as the solar radiation decreases the surface increases. This mathematical relationship is known as an inverse relationship (see definition of Cosine Projection Effect above).

Before Strategy/ Engage:

Group students by 2 or 3 to do the lab activity – in class.

Have students create flash cards of vocabulary and the essential questions. (This can be used to prepare for an assessment later.) I have students do the Vocabulary and Essential Questions the night before the lab activity so they are “pre-loaded” with some information prior to the activity.

Vocabulary:

Climate                   

Concentrated

Cosine Projection Effect

Fall equinox             

Infrared rays

Perpendicular          

Radiant energy

Radio waves           

Spring equinox

Summer solstice      

Troposphere

Ultraviolet rays        

Visible light.

Weather                   

Winter solstice

X rays

During Strategy/Explore/Explain

1. Tape the ruler along the side of the flashlight so that a 6-inch (15-cm) section of the ruler extends past the lamp end of the flashlight.

2. Lay the graph paper on a table.

3. Hold the flashlight perpendicular to the paper so that the free end of the ruler is on the edge of the paper and the flashlight is over the paper.

4. Darken the room and turn on the flashlight.

5. Place the thermometer in the brightest part of the light. Wait 2 minutes and then start recording the temperature (record the initial temperature and then record every minute for 5 minutes) on the data chart.

6. Observe the number of squares covered on the paper by the inner bright circle of light. Record the number of squares on the data chart.

7. Tilt the ruler down so the back end of the flashlight is about 6 inches (15 cm) above the table. Use the other ruler to help gauge distance and stabilize flashlight.

8. Place the thermometer in the brightest part of the light. Wait 2 minutes then start recording the temperature (record the initial temperature and then record every minute for 5 minutes) on the data chart.

9. Again, observe the number of squares covered by the light. Record the number of squares on the data chart.

Try New Approaches How does the curvature of the Earth affect the Sun's light rays?

10. Use the flashlight from the experiment; lay it on a table with the attached flashlight/ruler (the 6 inches are on the table) extending over the table edge.

11. Make a large cylinder out of the graph paper by overlapping the short ends.

12. Hold the cylinder vertically at the end of the ruler.

13. Place the thermometer in the brightest part of the light. Wait 2 minutes and then start recording the temperature (record the initial temperature and then record every minute for 5 minutes) on the data chart.

14. Observe the number of squares that are lit on the curved paper. Record the number of squares on the data chart.

15. Then move the cylinder slightly to the left or right so that the light grazes the edge of the cylinder. Again, observe the number of lit squares. Record the number of squares on the data chart.

Design Your Own Experiment

16. At this point, your group should discuss a good experimental design to answer the question as to why the atmosphere above the equator is warmest. Record your design procedures in the space below.

17. Using the materials that you have been provided, test your design procedure.

18. Sketch a simple illustration of your procedural setup (example: Figure 1 as an example)

19. Place the thermometer in the brightest part of the light. Wait 2 minutes and then start recording the temperature (record the initial temperature and then record every minute for 5 minutes) on the data chart.

20. Observe the number of illuminated squares on the paper. Record the number of squares on the data chart.

Student Data Chart 

After Strategy/Explain, Elaborate:

Graphing:

1. Using the data that was collected on the student data sheet, please create a line graph the time (x-axis) versus temperature (y-axis) for each of the 6 designs on the graph paper below.  Use a different color to represent each design.  *Create a KEY to indicate which design is which color. Also, ensure that you label the graph's axes and title correctly.

2.  Using the data from the student data chart, create a bar graph of the 6 designs (x-axis) vs temperature at 5 min (y-axis). Ensure that you label the graph's axes and title correctly.

3. Review the student data chart again, is there any other way to classify the data into a single graph? When your group has decided on the data and graph type, use the graph paper below to graph your information.  Ensure that you label the graph's axes and title correctly.

Laboratory Activity with graphing section   page 4

Assess/Evaluate:

The following Formative Assessment questions are the last step of the lab activity. This should be completed by the students in groups and turned in with their lab activity.

Formative Assessment Questions:

1. At this point, your group should be able to postulate a theory as to why, when roughly the same amount of light from the flashlight struck the paper each time, more blocks were illuminated when the light came in from an angle.

2. Why is the atmosphere warmer near the equator? (Use data from your investigation to support your theory.)

3. The number of daylight hour’s changes during the year. The more daylight hours during the day, the more radiant energy the Earth's surface receives. The day with the most daylight hours in the Northern Hemisphere is the first day of summer, which is on or about June 21. This day is the summer solstice. Find out more about the changing number of daylight hours during the year. (a) What and when are the spring and fall equinoxes, and the winter solstice? (b) How does the Earth's tilt cause different seasons? (c) What is the difference between the angle of the Sun's rays in the Northern and Southern Hemispheres on these dates (listed in a)? (d) What is the general difference in their atmospheric temperatures (use your cities data for the dates listed in Part A)? 

TABLE   page 5

Questions with Answers:

1. At this point, your group should be able to postulate a theory as to why, when roughly the same amount of light from the flashlight struck the paper each time, more blocks were illuminated when the light came in from an angle. “If the Sun is directly overhead (the angle of incidence of the Sun’s rays to the surface is 90°), the shadow has a smaller surface area of coverage.  If the Sun is lower in the sky (e.g., 30° angle of incidence), the shadow length increases and covers a larger surface area.”
2. Why is the atmosphere warmer near the equator? (Use data from your investigation to support your theory.) “If the Sun is directly overhead (the angle of incidence of the Sun’s rays to the surface is 90°), the shadow is of minimum size, and the sunlight is concentrated into a small area, the maximum amount of heating takes place, and higher temperatures result.”
3. The number of daylight hours changes during the year. The more daylight hours during the day, the more radiant energy the Earth's surface receives. The day with the most daylight hours in the Northern Hemisphere is the first day of summer, which is on or about June 21. This day is the summer solstice. Find out more about the changing number of daylight hours during the year. (a) What and when are the spring and fall equinoxes, and the winter solstice? (b) How does the Earth's tilt cause different seasons? (c) What is the difference between the angle of the Sun's rays in the Northern and Southern Hemispheres on these dates (listed in a)? (d) What is the general difference in their atmospheric temperatures?

Part A:                                                                                              Part C:

 Part B:       23.5^o tilt angle. 

“Many people believe that Earth is closer to the sun in the summer and that is why it is hotter. And, likewise, they think Earth is farthest from the sun in the winter. Although this idea makes sense, it is incorrect.  It is true that Earth’s orbit is not a perfect circle. It is a bit lop-sided. During part of the year, Earth is closer to the sun than at other times. However, in the Northern Hemisphere, we are having winter when Earth is closest to the sun and summer when it is farthest away! Compared with how far away the sun is, this change in Earth's distance throughout the year does not make much difference to our weather.  There is a different reason for Earth's seasons.  Earth's axis is an imaginary pole going right through the center of Earth from "top" to "bottom." Earth spins around this pole, making one complete turn each day. That is why we have day and night, and why every part of Earth's surface gets some of each. Earth has seasons because its axis doesn't stand up straight.”

Part D:             

Season                        General Atmospheric Temperatures (Alabama - Mobile) degrees F

2016 data                High                                                     Low                            Average

Spring equinox        72.2                                                     49.8                                  61              

Fall equinox            85.7                                                     71.3                                 78.5

Summer solstice     89.7                                                     66.2                                 77.95

Winter solstice       61.7                                                      41.5                                51.6

Part B:  https://spaceplace.nasa.gov/seasons/en/

Part A and C: https://www.wikipedia.org/

Part A and C: http://www.dictionary.com/

Questions 1 and 2:  https://www.nasa.gov/centers/langley/pdf/245895main_MeteorologyTeacherRes-Ch4.r3.pdf

Part D: http://www.usclimatedata.com/climate/mobile/alabama/united-states/usal0899

For a more Summative Assessment, the following questions can be incorporated into a quiz or into the COS 5 Unit test.

• Earth's tilt in combination with its orbit around the Sun causes the ____. ”seasons”

• Different seasons occur because of ____________________ and Earth’s orbital motion around the Sun. “earth’s tilt”

• If the tilt of Earth’s axis were increased from 23.5° to 30°, summers in New York State would become _____. “warmer, and winters would become cooler”

Base your answers to the following questions on the diagram below and on your knowledge of Earth science. The diagrams, labeled A, B, and C, represent equal-sized portions of the Sun’s rays striking Earth’s surface at 23.5° N latitude at noon at three different times of the year. The angle at which the Sun’s rays hit Earth’s surface and the relative areas of Earth’s surface receiving the rays at the three different angles of insolation are shown.

PICTURE   page 1

• As viewed in sequence from A (90^o) to B (66.5^o) to C (43^o), these solar path angles in the figure above represent which months and which change in the intensity of insolation? “June → September → December; and decreasing intensity”

• As the angle of the Sun’s rays striking Earth’s surface at noon changes from 90° to 43°, the length of a shadow cast by an object will ______. “ increase”

• What is Earth's axis?  “Earth's axis is the imaginary line around which Earth spins.”

• Why doesn't Earth's orbit cause seasonal temperature changes on Earth?  “The change in distance is actually minimal. Earth's tilted axis is the real cause of seasons on Earth.”         

• Predict which season this following scenario describes: The sun is directly above an object, at a right angle, the temperature is hot, and the sun spends more time in the sky due to its higher trajectory thus more heating occurs.  “Summer”

• What is the mathematical relationship between the sun’s angle (surface sunlight) and intensity and distribution? “As the angle increases the intensity decreases (inverse relationship) and the distribution increases (direct relationship)”

Acceleration/Elaborate/Extend:    

Switch your design with another groups design and evaluate each other’s design with the criteria below:

1. Following their procedure, would you be able to replicate their design? Please cite specifics on how to improve their procedures.

2. Evaluate their drawing of their design.  Does it adequately represent what they said to do in their procedures?  Please cite specifics on how to improve their drawing.  Please keep in mind not everyone is an artist.

Intervention: Here are some suggestions for students who need extra assistance:

Introduce the assignment in sequential steps

Check for student understanding of instructions

Check on progress often in the first few minutes of work

Provide time suggestions for each task

Provide a checklist for long detailed tasks

Assign a peer helper to check understanding of directions

Assign a peer helper to read important directions and essential information

Assign a peer tutor to record material dictated by the student 

Allow small group work