Bounce or Absorbed - Light Pathways and Interactions


Objectives:

Time Duration: four 50-minutes sessions

Grade Level: 8-11

Concepts Explored:
scientific processes, energy, communication, comparison, inference, classification, measurement, organization, evaluation and synthesis

Vocabulary:
radiant, incandescent, fickle foam, liquid crystals, heat, color, intensity, reflection, refraction, opaque, transparent, translucent, texture, surface.

Grouping: Groups of 4 or 5

Materials Per Group:

Materials Per Class:

Advanced Preparation:

Teacher Resources:

Teaching Tips:
Exploration of different materials for light refraction is important prior to teaching any terminology, such as opaque, clear, etc. The students will construct their own knowledge by discovery, comparisons and observations. Then, the meaningful contextual words can be taught.

Prior to Day 2, the students should have background on the solar system and the rotation of the earth. Activities with flashlights and students representing the sun and the earth would be appropriate. This lesson can extend into the upper grades to allow for discovery of the different angles of light as they reach the earth, by measuring the angles of light with a protractor. You may choose to use it as a demonstration, with guided questioning. Modify it to fit your grade level.

Procedure:
Day 1: Exploring the characteristics of light from different sources:

  1. Light a candle as a demonstration and ask students to record/share the characteristics they observe. Color, flame size, movement. Ask how far and in which direction is the light of the candle traveling? How can we find out? Depending on responses, you might facilitate the following discussion:

    • Darkening the room, and placing a white paper from gradually increasing distances away from the candle, (i.e. 5 cm, 25 cm, etc.) until the reflected light off the paper is no longer visible. Measure and record.
    • What else besides light is the candle emitting? How can we measure it? Place a thermometer near the flame, at 5 cm, then at 25 cm, record the temperatures, fill in a chart as a class model.

  2. Perform the same observations on different sources of light such as:
    • a flashlight
    • a desk lamp
    • a flood lamp
    • a fluorescent light
    • a halogen bulb
    • a colored light bulb (black, green, red, blue)

    Allow students to observe, measure and record their data in groups, then to share the information as a whole to reach conclusions.

    Make a sample chart like the one shown below on the board, to show students how to organize their data. For upper grades, you may ask students to design their own chart.

Light Source:         Observations          Distance beam         Temperature           
                                            traveled- visible                           
Candle                Blue on the bottom    5 cm: very bright     5 cm: ....C.deg. 25   
                      Yellow on top         25 cm: bright 50      cm:...C.deg. 50       
                      Orange center         cm: pale, dim 1 m:    cm:...C.deg.          
                      Shaped like an        very faint 1.5 m:     1m:...C.deg. 1.5      
                      upside down drop      slight trace 2 m:     ...m ...C.deg.: 2     
                      Smoke, flickering...  not visible           m:...C.deg.           
Desk lamp...

3. Based on the data gathered, what conclusions can be drawn? Which light is the most efficient? Why? What relationships can be drawn about the type of light, the heat it produces and the color it emits?

Assessment:
How do the light sources used in this exercise compare to the sun's light and the energy that reaches the Earth?

Invent an experiment with the lamp and thermometers which could help you understand more about how far heat (infrared) energy can travel.

Day 2: Analyzing the effects of light on matter/Earth:

  1. Recall the conclusions drawn based on the data gathering from the previous day. Explain to students that through the next exercise, they will be able to find out more about the effects of light on matter and how the sun's energy affects the Earth.

  2. To demonstrate how energy can affect matter, we will use one of the models widely known as sun sensitive paper. (It can be purchased through science supply houses, or use fax machine paper or paper from a photo lab/processing store). If any of these supplies are unavailable, use construction paper and expose for a longer period of time (perhaps a full day).
    • Place paper with an object or cut out figure covering a portion of its surface. Put a rock or other heavy item on top, so it won't be blown away by the wind.
    • Let the paper and object sit under the sun for 5-10 minutes. In the meantime, read the story "Sun Up, Sun Down", Scholastic Press. Discover the different ways light affects our daily lives.
    • Go outside and gather the papers, observe and record the changes.
    • Run the paper under water for a quick rinse and let it dry for another day. How will it look? What do you think happened to the paper? What might have happened if you left out in the sun for a longer period of time? A shorter time? How can this model teach us about the effect of the sun's energy and how it changes matter on Earth?

  3. Using the fickle foam, post card thermometers, globe and light source (flashlight or lamp), make a model of the energy of the sun reaching the earth as in Figure 1.


  4. Tape the postcards and fickle foam to the globe, one on the equatorial region and one near a polar region. Place a third one in between the other two. What does each object represent? Shine the lamp on it and record your observations. How does the light energy affect the liquid crystal cards or foam? What changes do you see?

  5. What does this tell us about the climate in polar, temperate, and equatorial regions of the world and the people who live there? What do they need to do to adapt to the changes in temperatures? How does incident solar energy affect the land, the agriculture, the homes in different areas?

  6. How else does the light energy of the sun affect us on Earth? Brainstorm and list.

Assessment:
How can the amount or intensity of light affect matter? How are color and light energy related? Make a model or invent an experiment using a light source and other objects to explain the effect of light on them.

Day 3: Explore reflection and refraction of light through different materials. Establish an analogy between the information gathered through the exercise and the use of remote sensing images.


  1. Recall how the light affected the different paper materials exposed to the sun's energy. Introduce the properties of reflection and refraction by guiding students to shine beams of light on and through different materials.
    • Give students squares of different cut out materials (listed under materials section, except the glass jars and water containers.)

    • Allow exploration to see how light would bounce or go through the different materials.

  2. Facilitate and motivate students into exploring how they could record and account for the differences between the materials and the way light passes through them or not. Make a graph of materials that allow light through, materials that don't, and those in between. Label the titles of the graph: Most Reflective, Most Refractive, Both Refractive and Reflective.

  3. What else besides light are the sources emitting? If light doesn't go through, where does the energy go? What does it turn into? Which tools would we need to record this change?

  4. Distribute the jars with liquid in them. Allow for exploration, observe and record information on the class graph.

  5. What conclusions can be drawn about the type of liquid in each jar, its characteristics and the amount of light that can travel through it or bounce off it? Share and record conclusions.

[Ask the students to suppose they are a fish that shoots jets of water by snapping its jaws closed at insects on low-hanging branches over the your pool of water. Your eyes remain below the water, but your target is above the water. What aiming adjustments do you, the fish, have to make in order to knock the fish into the water? Illustrate the aiming problem by placing a pencil in a jar of clear water and viewing it from the side. Have the students find the name and habitat of the actual fish that uses this form of hunting.]

Assessment:
If you were to live in _____ (a region of the earth), what type of materials would you use to build a house? Why?

Day 4: View remote sensing images.

Search for reflection and refraction clues. How is this information important for the study of our planet? Understanding the information gathered through remote sensing, based on the refractive and reflective properties of light and the types of effects it causes on different surfaces.

  1. View remote sensing color pictures depicting reflective light from different sources. Guide students in identifying the most/least reflective surfaces.

  2. Go to the playground and identify from the ground which objects would be identified as most reflective/refractive by a remote sensing plane flying above at a given altitude. (Low enough to identify buildings).

  3. Use thermometers outdoors to place on different surfaces exposed to the sun and record the temperatures. (Roof top, black top, bush top, fence top, grass area etc.). What else would be important information from the ground to identify the images from above? Would color of objects, weather conditions and time of day matter? Why? Record the conditions named and the temperatures to share with the class.

  4. Return to class and make a class graph to identify all the conditions needed for the analysis of the remote sensing images.

  5. Look again at the remote sensing images and see how many of the factors can be identified using the class chart. Did color, temperature, time of day and weather conditions have a role in the pictures being analyzed? What information can be seen on the remote sensing images that suggest these variables?

Assessment:
Give students the opportunity to make an experiment using dirt, leaves, water glasses, and fabric or paper on a foot square, exposed to the sun and record their information. Then they need to design their own miniature map as if seen from above, using the factors studied in the lessons.

Extensions:
Using transparent cups, dirt, water, sand and thermometers, students can build mini-biosphere regions for analysis of temperature and humidity factors. The cups can be placed at different locations for different exposure of the sun and the data gathered can be recorded over a period of time, for more accurate readings.

Example: Set up three cups, dirt filled, water filled and sand filled. Place a set of three each on a northern exposure window and a western exposure window. Record the temperatures of the cups over the Fall season and the Winter season. Project what might happen during the Spring season. How did the sun's light affect the cup biospheres? What temperatures surprises were found? How did they compare from north to west exposure? Why? At what time of day were the temperatures recorded? What would happen if they were measured during a different time? Is this a variable or a constant? Which would be your control? What other factors need to be taken into consideration when doing this experiment? ( room temperature, air conditioning, heater proximity, etc.)


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