Dab tsi yog qhov cuam tshuam ntawm emissivity rau qhov tseeb ntawm infrared ntsuas kub?
Peb paub tias thaum twg ib yam khoom nyob rau saum toj kawg nkaus xoom (-273.15 degree), nws nto yuav emit infrared zog, uas yog, infrared tawg. Qhov siab dua qhov kub, qhov muaj zog dua lub zog infrared! Infrared thermometers thiab infrared thermal imagers ntsuas qhov kub ntawm ib qho khoom nto raws li tus yam ntxwv no. Txij li thaum peb paub tias infrared thermometers thiab infrared thermal imagers ntsuas qhov kub ntawm cov khoom nto, lawv yog inevitably cuam tshuam los ntawm smoothness ntawm cov khoom nto. Cov kev sim tau pom tias qhov ze ntawm qhov khoom ntawm qhov chaw yog rau daim iav (nrog muaj zog xav txog), qhov hnyav dua qhov infrared zog attenuation emitted los ntawm nws nto. Yog li ntawd, peb yuav tsum tau them nyiaj rau qhov attenuation ntawm lub zog infrared ntawm cov khoom sib txawv, uas yog, teeb tsa tus nqi coefficient, uas yog emissivity!
Dab tsi yog qhov kev sib raug zoo ntawm emissivity thiab reflectivity
Kev tshawb fawb kho qhov muag pom tau hais tias thaum electromagnetic nthwv dej tshwm sim ntawm kev sib tshuam ntawm cov xov xwm sib txawv, lawv tau txais kev xav, kev xa mus, thiab kev nqus, ua rau:
+ρ+τ=1
Hauv cov mis: - absorption rate; ρ - reflectivity; τ - kev xa tawm.
Raws li Kirchhoff txoj cai, muaj:
=ε
Rau qhov opaque nto nrog τ=0, tom qab ntawd ε=1- ρ, nws tuaj yeem pom tau tias opaque nto nrog siab reflectivity muaj tsawg infrared emissivity. Qhov ntawd yog hais tias, qhov siab dua qhov kev cuam tshuam thiab nqus ntawm qhov chaw opaque, qhov qis dua qhov emissivity. Qhov siab dua qhov kev cuam tshuam, qhov tsawg dua qhov kub poob. Qhov no kuj muaj feem xyuam rau txoj hauj lwm ntawm lub vijtsam reflective thiab qhov chaw tshav kub.
