This is a parabolic cooker I built a while ago, so unfortunately I can't show step by step photos of it's construction. However, it's relatively easy to see how it was put together.
It makes a great science project. Unlike most, you'll actually get some use out of it afterwards. Some of the principles it demonstrates are:
1. Optics: focusing parallel rays of incident light through the use of a parabolic mirror.
2. Energy transformation: light to heat
3. Renewable energy: solar power
2 - 2x4 cut to 17" length (ends)
2 - 1/2" plywood cut to 1ft x 4ft (sides)
1 - 5/16" plywood cut to 18" x 4ft (backing)
1 - sheet of silvered mylar or tin foil cut to 17" x 4ft (mirror)
2 - 1/2" plywood cut to 3/4" x 12" (skewer mounts)
1 - 1/4" wooden dowel with a sharpened point (skewer)
Plus miscellaneous fasteners and spray adhesive
Screw driver bits
Step 1: Optics 101: Focussing light with a parabolic mirror
In order to focus parallel rays of incident light on a fixed point you need a parabolic mirror. There are a few different ways to generate a parabolic curve, but the easiest to understand (though not necessarily the easiest in practice) is simply doing the math.
The formula for a parabola is:
Y = X2/(4F)
X is the horizontal distance from the origin
F is the focal distance (a design choice)
Y is the vertical distance to the curve at any point X
See the image below for a graphical representation.