Experiment showing how a Fresnel lens in a lighthouse works to collimate light from a lamp into a parallel beam. The Fresnel lens, invented in 1822 by Augustin-Jean Fresnel, increased the light projecting power of lighthouses greatly without the weight of a conventional lens of its size. Also shown are mirror strips mounted above and below the lens that most lighthouses had, to gather more of the lamp's light.
Бездна
Lighthouse
@onkin
