Parabolic Reflectors
Parabolic Reflectors are curved mirrors shaped to aim all sunlight at a single spot.
A curved bowl can show why the shape matters. A flat surface bounces light at all angles, sending rays every which way. A bowl with just the right curve bounces every ray toward one spot above the center. Place a small ball at that spot, and lines from the rim to the ball all meet there.
Explaining parabolic reflectors by grade level
A flat mirror bounces sunlight in one straight line. A curved mirror shaped like a bowl can catch sunlight from a wide area. It sends all that light to one small spot. That spot gets very hot, enough to cook a hot dog.
Projects that explore parabolic reflectors
A parabolic curve lined with aluminum foil, shiny side out, reflects light toward a single focal point. You can find that spot by attaching posterboard to the opening and looking for the bright area where the light concentrates. Place a skewer through that spot and the sun's focused energy is enough to cook a hot dog.
A flat mirror bounces sunlight toward a solar cell but cannot focus it tightly. A parabolic dish covered with aluminum foil aims all its reflected rays at a single spot on the panel, concentrating more energy onto the surface. That tighter focus is why the parabolic reflector produces the highest power output, followed by the flat mirror.