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1、SummaryThestudentinvestigatesbasicpropertiesofspectrainthelabusingemissiontubesandspectroscopes.BackgroundandTheoryAstronomyisnearlyentirelyastudyoflight.Fromthissinglesourceofinformation,wecanoftenfindthephysicalconditions,compositionsandprocessesindistantobjects.Aplo
2、tofthebrightnessofanobjectversuswavelengthiscalledaspectrum,(pl.spectra),andisobservedusingaspectrograph.Byspreadingoutthelightbywavelength,wecangaininsightintowhat'shappeningtophotonsofparticularwavelengths(orenergies),whichinturntellsuswhat'shappeningwithparticularty
3、pesofatoms.Therearethreecomponentsofaspectrum:continuumemission(orblackbodyradiation),emissionlines,andabsorptionlines.·Continuumemissionisawide,smooth(continuous!)bandofcolorslikearainbow.Thistypeofemissioniscausedbyanopaquematerialwhichemitsradiationbecauseofitstempe
4、rature.Hotterobjectsarebrighterandbluerthancoolerobjects.Allobjectshavecontinuumradiation.(Evenyou;althoughinyourcase,sinceit'sintheinfrared,weusuallycallit'heat'.)·Anabsorptionlineischaracterizedbyalackofradiationatspecificwavelength.Absorptionlinesarecreatedbyviewing
5、ahotopaqueobjectthroughacooler,thingas.Thecoolgasinfrontabsorbssomeofthecontinuumemissionfromthebackgroundsource,andre-emitsitinanotherdirection,oratanotherfrequency.Absorptionlinesaresubtractedfromthecontinuumemission,sothattheyappearfainter.·Anemissionlineischaracter
6、izedbyexcessiveradiationatspecificwavelengths.Youcanobserveemissionlinesbylookingthroughaspectrometeratanenergizedgas.Theyarecreatedbythephotonsthatarereleasedbythe“falling”electrons.Theimportantthingtoknowaboutabsorptionandemissionlinesisthateveryatomofaparticularelem
7、ent(hydrogen,say)willhavethesamepatternoflinesallthetime.Andthespacingofthelinesisthesameinbothabsorptionandemission,onlyemissionlinesareaddedtothecontinuum,whileabsorptionlinesaresubtracted.Inthislab,youwillbeusingspectrometerstolookatvariouselementswhichhavebeenheate
8、dsothattheyhavemanyemissionlines.Youwillalsoobserveemissionfromcontinuumsources,andfromcombinationsofelements.Asyoulo
