The sun is a wonderful (and free) source of energy just waiting to be harnessed. You can build a simple solar hot dog cooker for use on a sunny day.
This hot dog cooker uses a reflective parabola. A parabola is a symmetric curve that resembles the letter “U.” The focus of a parabola is a point that lies along the axis of symmetry and acts as the special point around which a parabola (or any other geometric shape) is constructed.
Let’s practice finding the focus of the parabola. A parabola graphed using the equation y=ax2 must first be converted into standard form. Standard form for parabolas is as follows:
4p(y - k) = (x - h)2
Where h is the horizontal distance of the parabola origin (the curve) of the parabola from the point (0,0) and k is the vertical distance of the parabola origin from the point (0,0). 4p is equal to (1/a). This is just a mathematics convention.
We plug our numbers in to solve for p, which is the vertical distance of the focus from the parabola’s vertex, or lowest point.
So why would we need to use a parabola as our mirror, anyway? Here’s what’s so cool about parabolic mirrors: the focus is the point where all of the reflected light passes through. This makes a parabola a perfect mirror shape for cooking a hot dog.