物理演示實(shí)驗(yàn)牛頓環(huán)

Newton'sRingMethodtoMeasuretheRadiusofCurvatureoftheLens

Apparatusandappliances:Newton'sringsapparatus,sodiumlamp,readingmicroscope

Experimentalpurposes:1.Observationofequalthicknessinterferencephenomena,todeepenunderstandingofthevolatilityoflight.2.Learntoreadtheregulationanduseofthemicroscope.3Instituteofinterferencewiththeinterferencemeasurement,measurementofNewton'sringswithradiusofcurvatureofthelens

Experimentalprinciple:

First,theNewtonringinterference

Wecanseebythelightofthesuperpositionprinciple,whenthetwovibrationsinthesamedirection,thesamefrequencyandphaseconstantofthesuperpositionofmonochromaticlight,thelightintensitydistributionintheoverlayareaisuneven,butinsomeplacesagreatshow,andtheothersomeplacesshowingaverysmall,thisstabilityintheoverlayzoneinthephenomenonknownasthelightintensitydistributionofinterference.Toproduceopticalinterferencephenomenon,shouldmeettheabovethreeconditionstomeetthesethreeconditionsiscalledcoherentlightwaves.Toobtaincoherentlightisoftenthewaytothelightemittedbythesamelightsourceintotwobeams.Therearetwomethods,oneisthepartialwavevibrationsurfacemethod,oneisthesub-amplitudemethod.Partialwavevibrationsurfacemethodisthesamesurfaceofthelightwavevibrationisolatedtwoparts,thesamepartsofthesurfacewaveoscillatorhavethesamephase,whichwasisolatedpartofthesurfacewaveoscillatorphasecanbethesameastheearlylightphase,theselightphaseisconstant,sotheoverlayzoneinthetwobeamsoflightcanproduceinterference.Double-slitinterference,dualprismofinterventioninthiscategory.Sub-amplitudemethodistheuseofthetwosurfacesofthetransparentfilmfollowedbyreflectionofincidentlight,theamplitudeoftheincidentlightisdividedintotwoparts,resultingfromsuperpositionofthetwobeaminterference.Wedge,suchasNewton'sringsaresuchinterference,hereNewtonringinterferenceprinciple.

ShowninFigure1,willbealargercurvatureoftheconvexlensonaflatglasssurfacetoformaNewton'sringdevice,theconvexlensandtheplanebetweentheuppersurfaceoftheglass,formingathinlayerofair,inordertoaccessanypointasthecenterpointsonthecircumference,areequaltothethicknessofthinair.Thus,whenthewavelengthofthemonochromaticlightatnormalincidence,theairthinlayeroftheupperandlowersurfacereflectioninterferenceoftwobeamsofcoherentlightinterferencepatternformedbythecentershouldbeadarkspot,non-equallyspaced,concentriclightanddarkring,thisringiscalledNewton'srings.

Lettheradiusofcurvatureofplano-convexlens,theradiusfromthepointofcontactatapointonthecircumferenceoftheairlayerthickness,correspondingtothepointofinterferencegeneratedconditionsfortheformationofObscure

（1）

BythegeometryofFigure1canbeseen

（2）

Onthetypeofitemscanbeomitted,sotoo

（3）

Values??into(11-1)wassimplified

（4）

From(4),ifthewavelengthofmonochromaticlightisknown,butalsomeasuredtheradiusofthedarkring,wecancalculatetheradiusofcurvature.Conversely,ifknown,measured,inprinciplewecancalculatethewavelengthofmonochromaticlight.

SinceNewton'sringsandringthecenteroftheseriesisnoteasytodetermine,andthereforedonotuse(4)todetermine.Inactualmeasurement,often(4)intothefollowingform:

（5）

Whereandarethefirstlevelforthefirstlevelandthedarkringdiameter.Fromequation(5),aslongasthenumberofthemeasureddifferenceoftheringring,withouttheneedtodeterminetheprogressionofthering.Andcanprove,equalsthesquareofthediameterdifferencebetweenthesquareofthestring,andthereforecannotdeterminethecenterofthering,thusavoidingthecourseoftheexperimentisnoteasytodeterminecenterencountereddifficulties

Experimentalcontent

1.Opensodiumlamppowersupply,preheatfor10minutes.AdjusttheinstrumentNewton'sringsthreefixedshelvesscrews,adjustedtothecenterofNewtonrings,andthenplacedinthemicroscopeonthestage,andjustbelowitinthetube.

2.Sodiumlighttobeplacedbeforethemicroscope,bymovingthelocationandregulationofsodiumlightmicroscopeandahalfmirror,theentiremicroscopefieldfullofsodiumyellowlight.

3.Adjustthemicroscopeeyepiece,untilforkcanseeaclearcross-wire,andthenadjustthelensfocusadjustmenthandwheel,untilyoucanseeaclearNewtonringinterferencepattern.

4.Micrometerdrumturning,wiretransferforktothecenterofNewton'srings,andthenleftto25Obscureleft.Atthistime,lettherightforkmovesslowlytowardthewire,andwireweredownforkwiththefirstleveland10,9,8,7,620,19,18,17,16darkstripesontheleftoutsidethecutlevelwhenthepositioncoordinates,andthencontinuerighttocrosswire,andthenwritedowneachwirewithcrosssection6,7,8,9,1016,17,18,19,20andoutsidethecutattherightlevelObscurecorrespondingpositioncoordinates,themeasureddatarecordforms.

Experimentaldata

Measuredradiusofcurvatureofconvexlensdatatable

Ringnumberreadings/mmdiameter/mmringnumberreadings/mmdiameter/mm

mleftrightleftrightDmnDnmm2

2025.78319.11024.88520.0134.8726.6731020.79

924.7881925.70019.1936.50720.1284.66020.62

1825.62019.2856.355824.67920.2474.43220.49

71725.54119.3656.17624.56020.3644.19620.54

1625.45419.45224.44820.5023.9466.002620.45

(m)

0.8%

0.8%×0.87=0.007(m)

=0.8730.007(m)

rimenteasyproblems

1measuringhandwheelmustnotreversetheprocess.

2wirewithcross-Newtonringsideoftheforkwithinthecut,whileoutsidethecut.

[Thinkaboutquestionsandanswers]

Equalthicknessinterferenceischaracterizedbywhat?Iftheinterferencepatternofdistortiontowhat?

Equalthicknessinterferencecharacterizedbythecontactpointasthecenterofthebrightanddarkconcentricrings,thecentraldarkclasses,withthefringeorderincreases,thefringespacinggrowseverwider.InterferencepatterndistortionDescription:plano-convexlensandtheglassplateofthecontactpointsduetomechanicalpressure,dust,causedbydefects.

2.IfthecenterofNewton'sringsarebrightspots,theradiusofcurvatureofthelensmeasuringinfluential?

Becausethedifferencemethodusedbydataprocessing,soNewton'sringsarebrightspotscenter,radiusofcurvatureofthelenshadnoeffectonmeasurement.

3.Whyinthemeasurementoftheradiusofcurvature,youcanusetwochordinsteadofasmallringdiameteriscalculatedtoproveit.

Tip:concentricringsinthesquareofthediameterofaquarterch