A flashlight projects light in one general direction because of the reflecting surface behind the lightbulb. This redirection of light is called collimation, a fine SAT word if I've ever heard one. A good flashlight collimates more of the bulb's light than a poor one. How well a flashlight collimates depends on the shape of the reflecting surface and on the distance of the bulb from the surface. Which shape is the collimation champion? This application compares the light-reflecting properties of four different surfaces: Parabolic Spherical Quartic Conical