Lesson: Direct and Diffuse Light
Prerequisites:
None
Objectives:
Create an understanding of the difference between direct and diffuse light
Materials:
- watercolor paints
- paper (white)
- posterboard
- flashlight
- popcorn (uncooked)
- cup
Introduction:
Teacher starts by shining the flashlight onto the posterboard first perpendicular to the board and then at an angle. The teacher asks: "Which light is brighter?" "Why? Have we changed the brightness of the flashlight?"
Body:
- You will need a flashlight and a piece of posterboard. Have the class sit in a semi-circle around you and hold the posterboard so that everyone can see it. Dim the lights and shine the light on the board so that the light is perpendicular to the board. Ask a student to outline the pattern the light makes on the board. Shine the light at a shallow angle to the board on a different area of the board. Ask a student to outline the pattern the light makes. Now ask the class what they notice. Possible questions are:
- Describe the shapes of the outlines.
- Which outline is larger?
- Which outline has the bigger area or takes up more space?
- Which pattern is brighter or more intense (may need to repeat the demonstration)?
- Which light is more diffuse, less intense, or more spread out?
- Divide students into groups of three or four. Each group will need watercolors and a piece of non-absorbant white paper. Have the students fill in both the circle and the oval with water using their paint brushes.
Next, have one student dip the brush in the blue paint. The student should make seven drops in the circle of water. Have the next student make seven drops of blue paint in the oval of water. Ask each group to make observations about their circles and ovals to share with the class. Some possible questions are:
- Which shape has the brighter (more concentrated) color, the circle or the oval? Why?
- Which pattern covers more area?
- In which shape is the color more spread out, or diffuse?
- Group students into groups of three or four. Each group is given two styrofoam cups with the bottom one-quarter inch filled with uncooked popcorn. On a plain piece of paper have one student pour the cup of corn out slowly and carefully to make a small circle of popcorn. Have a student draw a circle around the popcorn kernels. On a larger sheet of paper have another student pour out the second cup of corn more quickly so that the corn spreads out on the paper. Have a student draw a line around perimeter of the pattern of popcorn. Ask each group to discuss what they notice about the shape of each popcorn pattern. Some possible questions are:
- Describe the shape of the popcorn pattern.
- Which pattern is larger?
- Which pattern has a bigger area (takes up more space)?
- Which pattern has the popcorn more concentrated?
- Which pattern is the popcorn more spread out (or diffuse)?
Conclusion:
What simularities have you noticed between the experiments we have done today? Summarize the popcorn, watercolor and flashlight experiments. Possible answers:
- Smaller circles or areas were brighter, more concentrated or more intense.
- Larger circles or patterns were more spread out, diffuse, or less intense.
Vocabulary Words:
- diffuse
- concentrated
- direct
- intensity
Evaluation:
- Listen to discussion of conclusion for student's ideas and redirect if needed.
- Prepare a sheet asking what students noticed and include vocabulary words.
- Have the students make a picture or painting showing the concepts of diffuse and direct.
Followup Lessons:
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