Thaum ib lub teeb ntawm lub teeb sib txuas nkag mus rau qhov nruab nrab (xws li cov yas pob tshab), lub teeb lub teeb hloov kev coj mus rau -kev sib kis thiab deflection-vim inhomogeneities hauv cov khoom siv kho qhov muag, xws li qhov chaw tsis xws luag, sab hauv cov qauv tsis zoo, thiab muaj cov npuas lossis impurities. Qhov tshwm sim ntawm lub teeb tsis zoo yog hu ua * tawg tawg *.
Thoob ntiaj teb, * haze * txhais tau tias yog qhov piv (qhia raws li feem pua) ntawm cov luminous flux tawg ri niab- uas deviates los ntawm cov kev taw qhia ntawm qhov teeb meem teeb tom qab dhau los ntawm ib tug qauv - mus rau tag nrho cov kis luminous flux. Cov qauv uas pom muaj haze siab tshwm sim ntau qhov muag plooj rau cov neeg soj ntsuam.
Lub teeb kuj undergoes attenuation thaum nws dhau los ntawm tus qauv; tshwj xeeb, qhov kis luminous flux tawm los ntawm cov qauv no tsis tshua muaj qis dua qhov xwm txheej luminous flux impinging rau nws. Qhov piv ntawm ob qhov tseem ceeb no, qhia raws li feem pua, yog thoob ntiaj teb txhais tias yog * kis * .
Cov yam tseem ceeb uas ua rau muaj kev txo qis hauv kev xa tawm muaj xws li qhov cuam tshuam ntawm lub teeb ntawm cov qauv ntawm ob qhov chaw, nrog rau cov qauv kev nqus ntawm lub teeb lub zog- nyob rau hauv tag nrho cov spectrum los yog ntawm cov wavelengths tshwj xeeb - los ntawm cov teeb meem kab teeb.
Thaum lub sij hawm tus txheej txheem ntawm kev soj ntsuam ib tug specimen lub haze thiab transmittance, nws yog ib qho tseem ceeb los ntsuas qhov teeb meem luminous flux (T1), kis luminous flux (T2), lub twj paj nruag intrinsic luminous flux (T3), thiab cov specimen luminous flux (T4).
Kev ua cov ntaub ntawv yog ua raws li "DRTG-81 Test Method." Txoj kev suav rau kev xa khoom siv los ntawm qhov ntsuas no yog raws li hauv qab no:
Transmittance: Tt=(T2 / T1) × 100%, qhov twg T1 yog teem rau 100.
