SCI201 Lecture Notes - Lecture 8: Radiant Flux, Black Body, Emissivity

• School: University of Waterloo
• Department: Science
• Course: SCI201
• Professor: Yuri Leonenko

Document Summary

Radiation of incident power p0 can be absorbed by the air sample, resulting in a transmitted beam of lower radiant power p: absorbed amount = fp0 transmitted amount = (1-f) p0. Incident radiant (ir) p0 transmitted radiation p: black body if totally absorbed. We cannot think of earth radiation as being radiated into space directly from the surface. Much of the radiation emitted from the surface will be absorbed, primarily by. There is regions or layers in atmosphere which absorbs earth radiation (s. 4) Because the surface getting more incoming radiation than if the atmosphere were not present (or were completely transparent to ir) the temperature of surface is higher. This has become known as the (cid:862)g(cid:396)ee(cid:374)house effe(cid:272)t(cid:863). (cid:894)s. 4(cid:895) (slide 7) s surface; earth radiation atmosphere is black body. Ki(cid:396)(cid:272)hhoff"s la(cid:449): at a(cid:374)y spe(cid:272)ifi(cid:272) (cid:449)a(cid:448)ele(cid:374)gth of a(cid:271)so(cid:396)pti(cid:448)ity e(cid:395)uals e(cid:373)issi(cid:448)ity of this wavelength fractional absorptivity equals fractional emissivity, at all wavelengths. Our atmosphere is very close to the globe (slide 13)