S Tolansky and W K Donaldson 1947 J. Sci. Instrum. 24 248 doi:10.1088/0950-7671/24/9/308
S Tolansky and W K Donaldson
Show affiliationsThe reflectivities of electrodeposited speculum (a copper-tin alloy containing preferably 45% of tin) and of speculum prepared by evaporation in vacuo have been determined over the range 4500-6500 A. The reflectivity of the freshly polished electrodeposited alloy containing 45% of tin, which is the ideal composition from the viewpoint of maximum resistance to tarnishing, varies from 63% at 4500 A. to 75% at 6500 A. After keeping for six months in a damp atmosphere the reflectivity decreases by 10% in the red region and by 2% in the blue region. Evaporated speculum on a glass base has a reflectivity of 68% at 4500 A. increasing to 78% at 6500 A. The higher reflectivity of evaporated speculum as compared with electrodeposited speculum of the same composition is attributed to the greater perfection of the evaporated mirror surface and consequent reduction in the amount of non-specular reflexion.
78.20.-e Optical properties of bulk materials and thin films
Issue 9 ( 1 September 1947)
Received 9 December 1946
S Tolansky and W K Donaldson 1947 J. Sci. Instrum. 24 248
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