实验八辐射定律实验目的：验证辐射定律预备知识热量的传递方式黑体的概念热电偶的测量原理实验概述我们将物体的各种温度所释放出来的辐射称为热辐射，所有的物体都对外界释放这一辐射能，也从外界吸收此种辐射。如果一个物体比它的外界热，它就会因释放出來的能量比吸收的能量多而变冷，一般情况下受热的固体辐射出的电磁波，其强度及强度对频率的依赖关系与温度及固体的性质都有关。但是当物体处于热平衡状态，热的吸收率和放射率一样的時候，它对电磁波的吸收和辐射达到了平衡，电磁辐射的特性将只取决物体的温度，与物体的其他性质无关。即斯特藩－玻耳兹曼定律：（：辐射通量密度，单位时间内通过单位面积向一侧辐射的总辐射能量）如果一个物体在任何温度下都能够把投射到它上面的任何频率的电磁波全部吸收，这个物体就称为绝对黑体。带小孔的空腔可看作一个绝对黑体，故空腔中的电磁辐射也称为黑体辐射。图1实验原理Allbodiesradiateheat.Theintensityofthisthermallyexcitedelectromagneticradiationincreaseswiththetemperatureofthebody,andisalsodependentonthesurfaceofthisbody.Atagivenwavelength,themoreheatabodyradiates,thebetteritcanabsorbthisradiation.1Abodywhichcompletelyabsorbsheatradiationofallwavelengthsiscalledablackbody.ItwasKirchhoffwhofirstproposedusingacavityasavirtuallyidealblackbody.Theblackbodyhasthegreatestabsorptionfactor,andthus,atagiventemperatureandwavelength,thehighestpossibleemissivityaswell.TheStefan-BoltzmannlawstatesthatthetotalemittedradiationofablackbodyincreasesproportionallytotheabsolutetemperatureTraisedtothefourthpower.Moreprecisely,theradiantexitanceM,i.e.thetotalpowerradiatedononesideofthesurfacewithreferencetotheareaoftheradiatingsurface,isdefinedasM=T4(I)(=5.6710–8K-4Stefan-Boltzmannconstant)Atthesametime,theblackbodyabsorbsradiationfromitsenvironment.Thus,wedonotmeasurethetotalradiatedradiantexitanceM,butrathertheradiantexitanceM’withdrawnfromtheblackbodybyradiation.TheradiantexitanceabsorbedfromtheenvironmentisM0=T04(II)Therefore,itfollowsthatM’=(T4–T04)(III).Inthisexperiment,anelectricovenwithablackbodyaccessoryisusedasthe“blackbody”.Theblackbodyaccessoryconsistsofaburnishedbrasscylinder...
