Diffraction grating

Diffraction gratings, sixteen, from about 1925

Diffraction grating

Diffraction grating, 5 1/16 inch, on speculum in wood frame, in wooden box, ruled by Theodore Schneider on Henry Rowland's engine, Baltimore, USA, 1883 - the surface of the grating must NEVER be touched, not even with gloves

Diffraction grating

Diffraction grating, one of sixteen, speculum metal, round surface 105 mm diameter in wooden case, ruled at National Physical Laboratory on Blythswood machine, no 60055, September 1938

Diffraction grating

Diffraction grating, one of sixteen, No 62333, concave grating of 2 m radius on round glass plate 4 ¼” diameter, coated, ruled test stripe below the curved bottom edge of the grating, in wood and Perspex cell, 1947