Self-made solar cooker
Find a concave reflective bowl on a big flashlight, and cut it into a cylinder about 4 cm long with rigid foam plastic or wood, just enough in diameter to fit into the round hole of the reflective bowl. Drill a fine hole horizontally at one end of the cylinder, insert an iron wire with a diameter equivalent to the aperture, and then bend the two ends of the iron wire exposed outside the cylinder at 90 degrees, leaving 5 cm each. Insert the cylinder into the round hole of the reflective bowl, and then insert both ends of the iron wire on the foam plastic or wooden bottom plate. Sharpen both ends of a thin bamboo stick, insert one end into the cylinder in the center of the reflective bowl, and insert a small piece of potato at the other end. Put the device in the sun, let the reflective bowl face the sun, and then, patiently adjust the length of the bamboo stick so that the inserted potatoes are just in the focus of light. Before long, the potatoes will be cooked by the sun and smell delicious.
2. Seek small-scale technical products (the simpler the better)
You can make a kaleidoscope. (Using optics to make simple scientific and technological production, suitable for primary and secondary school students) The practice is as follows:
Use two glass strips about15cm long and 3cm wide (you can buy scraps from the glass shop). Cut another piece of cardboard the same size as the mirror strip and paint one side black. As shown in the figure, combine two mirror strips with a piece of cardboard (the black side of the cardboard faces inward), stick them with adhesive tape, and then tie them tightly with two rubber bands. This becomes the simplest kaleidoscope.
Put some colored paper and colored glass beads on a piece of white paper. Look at them through the kaleidoscope, and you will see many star-shaped patterns. Turn the kaleidoscope and the pattern will change accordingly.
If there are no glass strips, glass strips can be used instead, but one side of the glass should be painted black or pasted with black paper, with the black side facing outward. However, the kaleidoscope made of glass strips looks much brighter than that made of glass strips.