[填空题]
The sun radiates energy to the much+c,c;sxtf 0 d 70ksurface of the earth. Somep(v :qarh5. 6ut xi muwxg5i)elz u(5/ of this energy is scattered and the rwm( (xu)u ./ghe5t vq6 pr5zx:l5ia iuest reaches the earth's surface.
1.Differentiate between heat transfer methods: conduction, convection and thermal radiation.
2.At any given time, the power of the radiation of the sun absorbed by the earth's surface is $P$.
$P$is given by
$P\,=\,(1−α)SπR^2$
Where $α$ is the albedo of the earth’s surface.
(1)Show that the average intensity of radiation $I_{avg}$ that is absorbed by the earth's surface is given by $I_{avg}$=$\frac{(1−α)S}{4}$.
(2)Calculate the average intensity of the radiation that is absorbed by the earth's surface. The earth's albedo is 0.3. $I_{avg}$ = $Wm^{-2}$
Some of the infrared radiation from the earth is absorbed and reradiated by the greenhouse gasses.
3.Explain this absorption and emission of radiation in terms of molecular energy levels.
