Jasper County Democrat, Volume 10, Number 44, Rensselaer, Jasper County, 1 February 1908 — FOR THE CHILDREN [ARTICLE]

FOR THE CHILDREN

An Achromatic Lens. Many of the boys and girls no doubt have read or heard of an achromatic lens without knowing exactly what the term means, says the Chicago News. It means a lens that transmits light without dividing it into its constituent colors. A ray of ordinary light is composed of the seven colors of the rainbow, as Sir Isaac Newton showed us by the use of the prism, each color having a different degree of refrangibility. When a direct ray is refracted, therefore, it divides itself into the colored rays, which deviate variously from the straight line of the simple ray and thus surround the object viewed with a halo of those colors. It was thought for a long time that this defect could not be remedied, but about 1750 a man named John Dolland made an improvement that accomplished the desired purpose. He found that flint glass and crown glass differ in their power of dispersing colors, and he made a double lens of flint glass, and the combination of the two gives an almost colorless image. The achromatic lens is of great value to astronomers and also to users of the microscope.