David Brewster (1781-1868), Scottish physicist. Brewster was a child prodigy, and studied for the ministry of the Church of Scotland. Because he was afraid of speaking in public, he turned instead to the study of optics. He received an award in 1816 for his equation for Brewster's Angle, an angle to maximize reflected light polarization. His other advances in optics included the polyzonal lens (1811) that improved lighthouse lights. He is best remembered for his invention, in 1816, of the kaleidoscope. Millions of the toys were sold. His work on polarization has numerous applications in fibre optics, lasers, microscopy and radio. He was knighted in 1832.