How Big Is That Picture?
Students gain a perspective of field of vision from a great height.
Grade Level: 4-5
Time Duration: Two or three class periods
Concepts Explored: Scale and structure
Suggested grouping: class demo with student helpers
- toilet paper or paper towel roll
- small flash light with a strong beam (a magnetite or halogen variety
- that will fit in the roll
- piece of opaque paper to cover bottom of the roll; punch a hole in the
- middle with a paper punch; attach the opaque cover to the bottom of
- the roll with a rubber band
- tape measure
- dark marker
- darkened room ideally a gym with a basketball hoop
- Secure the flashlight in the paper roll with tape. Cover the open end with
the opaque paper with the hole to mask the bottom of the roll.
- Have students lay out the rope, measure off one foot sections and clearly
mark them. If you are using a basketball hoop you will need about 25 feet of
- Tape the flashlight-roll assembly very securely to the rope.
- During this time the other students can prepare a worksheet with three
columns: height, diameter circumference.
- Review the concept of diameter with the students.
- Throw the selvage end of the rope through the hoop.
- Turn on the flashlight and have the students observe the size of the circle
of light when it is just above the floor.
- Have a student pull the rope so the tube moves up one foot (to the first
mark). Have another student measure and record the diameter of the circle and
the height of the flashlight.
- Continue to measure foot by foot to 15 feet. A pattern will emerge.
- Teach the children to find the circumference of the circles. It is okay to
approximate and multiply by 3 (instead of the full value of pi). Find
the circumference of each and chart it.
- Using proportion, find how big the circle would be at 100 feet 1,000 feet
10,000 feet and so forth.
- Aircraft used for remote sensing fly at altitudes between 9,000 and 12,000
feet for low-altitude aircraft, 65,000 feet for high-altitude aircraft and
satellites as high as 400 or more miles.
- How many feet are in 400 miles? What would the diameter of the circle cast
by the flashlight be at that height?
Have your students convert all the measures in this exercise to metric units.
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