Description

George Russell Harrison poses with a 10-inch diffraction grating, used in the study of light. Stamp on verso reads "Mar 28 1958". Original caption: "Dr. George R. Harrison, Dean of Science at the Massachusetts Institute of Technology, with a 10-inch diffraction grating, the largest and most perfect ever made. In the mirror surfaces of a glass block are 74,500 parallel grooves, ruled by a machine at M.I.T. to an accuracy of a millionth of an inch. The grooves break light into a spectrum so that it can be analyzed."