నిమ్రద్ కటకం: కూర్పుల మధ్య తేడాలు
Content deleted Content added
K.Venkataramana (చర్చ | రచనలు) దిద్దుబాటు సారాంశం లేదు |
K.Venkataramana (చర్చ | రచనలు) దిద్దుబాటు సారాంశం లేదు |
||
పంక్తి 16:
}}
==వర్ణన==
The [[lens (optics)|lens]] is slightly oval, and was roughly [[Grinding (abrasive cutting)|ground]], perhaps on a [[lapidary]] wheel.<ref name="layard"/> It has a [[Focus (optics)|focal point]] about {{convert|4.5|in|cm|disp=flip}} from the flat side, and a [[focal length]] of about 12 cm.<ref name="layard"/><ref name=Brewster>{{cite journal | journal = Die Fortschritte der Physik | publisher = Deutsche Physikalische Gesellschaft |year=1852 | author = D. Brewster | title = On an account of a rock-crystal lens and decomposed glass found in Niniveh |language=German | url = https://books.google.com/?id=bHwEAAAAYAAJ&pg=RA1-PA355&dq=niniveh+lens }}</ref><ref name=bm/> This would make it equivalent to a 3× magnifying glass. The surface of the lens has twelve cavities that were opened during grinding, which would have contained [[naphtha]] or some other fluid trapped in the raw crystal. The lens is said to be able to focus sunlight although the focus is far from perfect. Because the lens is made from natural rock crystal the material of the lens has not deteriorated significantly over time.<ref name="layard">{{cite book|last=Layard|first=Austen Henry|title=Discoveries in the ruins of Nineveh and Babylon: with travels in Armenia |year=1853|publisher=G.P. Putnam and Co|pages= 197–8,674 |url=https://books.google.com/?id=1KITAAAAYAAJ&pg=PA674&dq=british+museum+lens+layard#v=onepage&q=lens&f=false}}</ref>
|