This project is for older students or for younger students with adult supervision.

A reflective hot dog cooker can be built from a cardboard box, tin foil, and posterboard. Sunlight hits the reflective surface and focuses on the hot dog held in the center. Students can work in pairs or individually if there are enough materials.

  1. A cardboard box
  2. tin foil
  3. posterboard

Select a long narrow box; the longer the box the more heat collection is possible. Choose a focal length between 5" and 10" and design a parabolic curve as seen in the picture. One template could be used for all the cookers. Trace the curve on the open end of the box so that it is centered and straight.
Cut out the curve with a utility knife. Stress the importance of being exact. Measure and cut a piece of posterboard that will fix flush against the opening to the box. Attach this with tape beginning at the center and working toward to edges.
Cover the curve with white glue and apply aluminum foil shiny side out. Start in the middle and smooth toward the edges. Try not to wrinkle or fold the foil; you want it as smooth as possible.
Use two scraps of cardboard taped to each side as supports. Using the sun or a projector light, test the focal point. There should be a bright spot where light is concentrated; mark this spot and punch a hole for the skewer. Use a section of a coat hanger from which the paint has been removed for a skewer.
Enjoy your hot dog!


Hot Enough to Fry an Egg

You can also use the heat of the sun on a sidewalk or on black asphalt.

Take three eggs, two black/cast iron frying pans, and one piece of thick glass to cover one of the frying pans.

Put one egg directly on the sidewalk, one in the pan without the glass cover, and one in the pan with the cover. Which one do you think will fry the quickest. Make sure you clean up afterwards!



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