apparatus apparatus term refer types instrument historically measure speed light instrument types arises originally friends collaborators worked projects process images sun absorption bands infrared spectrum sunlight developed method rapidly rotating mirror study phenomena applied method measure velocity electricity wire duration electric spark communicated idea method adapted study speed light expanded concept publication emphasizing possibility test relative speed light air versus water distinguish particle wave theories light suggested attempt measure speed light appears falling parted ways pursuing separate means performing experiment rotating mirror toothed wheel apparatus perform absolute measurement speed light air rotating mirror devices perform relative measures speed light air versus water scaled version rotating mirror apparatus perform absolute measurement speed light subsequent experiments performed improved versions toothed wheel rotating mirror experiments steadily accurate estimates speed light determination speed light determined speed light intense light source mirror distant light source interrupted rotating rotated variable speed hundreds times second figure adjusted rotation speed light passing notch completely eclipsed adjacent tooth spinning times basic rotation rate resulted reflected light teeth line given speed wheel distance wheel mirror able value speed light difficult visually estimate intensity minimum light blocked adjacent teeth value light speed high early mid 1800s period intense debate particle versus wave nature light observation spot settled matter definitively favor wave theory light concerns continued appear addressed newton theory suggested differential comparison speed light air versus water serve prove wave nature light racing establish point engaged build mirror apparatus split beam light beams passing water traveled air beaten mere seven weeks confirmed speed light greater traveled air wave theory light determination speed light improved speed light rotating mirror toothed wheel figure apparatus involves light reflecting rotating mirror forming image distant stationary mirror reflected reform image original mirror stationary image reform regardless mirror tilt situation different rapid rotation rotating mirror moved slightly time takes light bounce light away original source small angle seen figure displaced image source angle source direction guided similar motivations partner interested settling particle versus wave debate determining accurate absolute value speed light measured differential speed light versus water tube filled water rotating mirror distant mirror experimental results announced shortly announced results topic viewed driving nail coffin newton theory light showed light travels slowly water air newton explained pull medium light implying increased speed light medium theory light went completely overshadowed wave theory state affairs lasted presented arguments circumstances considering effect light exhibits behaviors indicative particle nature contrast measurement measurement aimed obtaining accurate absolute value speed light concern improved value astronomical unit time working paris observatory belief based extensive mechanics calculations consensus value speed light high technical limitations prevented separating mirrors meters despite limited path length able measure displacement image considerable accuracy addition unlike case experiment required rotation rate speed toothed wheel spin mirror constant determined speed measurement confirmed estimate figure speed light modern value experiment behest paris observatory repeated toothed wheel measurement series experiments goal obtain value speed light accurate thousand equipment allowed monitor high orders extinction 21st order instead estimating intensity minimum light blocked adjacent teeth relatively inaccurate procedure pairs observations intensity averaging values obtained wheel spun clockwise electric circuit recorded wheel chart enabled precise rate comparisons observatory clock telegraph key arrangement allowed mark chart precise moments judged extinction entered exited final experiment run path nearly times long yielded figure modern value experiment seen figure placed rotating mirror close possible lens maximize distance enlarged image sweeps face distant mirror greater distance quickly image sweeps mirror light reflected increase distance folded optical arrangement meters image dim accurately measure multiple measurements speed light measurements performed auspices working measuring speed light setup incorporated original arrangement seen figure placed rotating mirror near principal focus lens focal point given incident parallel rays light rotating mirror exactly principal focus moving image remain distant plane mirror equal diameter lens long axis pencil light remained lens true regardless distance able increase distance nearly feet achieve reasonable value distance extremely long focal length lens feet compromised design placing feet closer principal focus allowed distance feet carefully tuning monitor rotation rate air turbine powered mirror typically measure image order figure speed light modern value repeat experiment incorporated use shaped rotating mirrors enabling brighter image having sixteen mile surveyed parts million accuracy figure higher current accepted value final attempt measure speed light vacuum interrupted death experiment completed posthumously factors measurement highest accuracy including earthquake disturbed measurement relative speed light measurements sur aide des des sur les relatives air par sur experience relative comparative air absolute speed light measurements sur experience relative propagation des surfaces des classroom demonstrations speed light method modern experiment education outreach purposes measuring speed light video method astronomy
Fizeau–Foucault apparatus