 Descartes proceeds to deduce the law of refraction. The ball is struck by the racquet at A and moves along AB until it strikes the sheet at B. Where will the ball land after it strikes the sheet? Descartes stipulates that the sheet reduces the speed of the ball by half. Consequently, it will take the ball twice as long to reach the circumference of the circle after impact than it did for the ball to reach the surface at B. We also know that the determination of the ball in direction AB is composed of two parts, a perpendicular component determination (AC) and a parallel component determination (AH). Descartes reasons that 