About: http://webisa.webdatacommons.org/172226158

Property	Value
http://www.w3.org/1999/02/22-rdf-syntax-ns#type	http://www.w3.org/ns/prov#Entity
http://www.w3.org/ns/prov#value	When you have an obstruction, like the edge of a table leg, for example, it lis like half a slit and light coming from the edge is restricted to come mostly from one direction.
http://www.w3.org/ns/prov#wasQuotedFrom	askthephysicist.com