Lesson: Direct and Diffuse Light




Create an understanding of the difference between direct and diffuse light



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?"


  1. 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:

  3. 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:


  5. 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:


What simularities have you noticed between the experiments we have done today? Summarize the popcorn, watercolor and flashlight experiments. Possible answers:
  1. Smaller circles or areas were brighter, more concentrated or more intense.
  2. Larger circles or patterns were more spread out, diffuse, or less intense.

Vocabulary Words:


  1. Listen to discussion of conclusion for student's ideas and redirect if needed.
  2. Prepare a sheet asking what students noticed and include vocabulary words.
  3. Have the students make a picture or painting showing the concepts of diffuse and direct.

Followup Lessons:

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