 Now let's put our diagram into action. So we've already learned our shorthand that a surface emitting light is going to have a curved arc. If the light coming out of that surface is shortwave, it's going to be a straight line. From a different surface, this is going to be some surface at temperature one. A different lower temperature surface is potentially a very good longwave emitter. Also having a curved arc for the emitting surface and a wiggly line, in this case full, that signifies that longwave band that's that band greater than 3,000, 3,000 to 50,000 or 3,000 to 30,000 nanometers. Whereas the shortwave is at 250 to 2500 nanometer range. Any other notations we're going to come across here in just a second, you can see here I've got a diagram of the sky dome. This is pretty common arc that we're going to have in the class. Just saying that there's this entire sky here and it in and of itself is going to be a source of light. How do we diagram that? Well, first let's put a receiving surface on the ground. We'll say that we have a solar panel on the ground here and it's going to be a receiver of light. I'm going to now start diagramming. I know that the sun is a source of emission of light that's going to be shortwave light. Shortwave light, as we will see in just a second, is effectively transparent to the atmosphere. So it's passing straight through the atmosphere without being absorbed and ultimately it's going to come to the surface. A portion of it might reflect off. The rest of that light is going to be absorbed by our solar collector and thus generating excited states for electrons. If it's a photovoltaic panel, hot water, if it's a solar hot water system. That's our main source of energy that we think of and that's that beam component of light that we'll talk about eventually. There are other sources of light in this system and we want to diagram them. For example, we know that the sun will hit the ground and it'll reflect off the ground. We're going to have a lot of light that's coming and hitting the ground and reflecting off of it. And that reflected light off of the ground is called the albedo. But in our case, we're just diagramming it as a check mark on here and it will ultimately also be a secondary but a source of light for this tilted panel. That's the participation of the ground in the shortwave energy. The sky itself is full of backscattering, right? We had this diagram of forward scattering and backscattering across the atmosphere. I'm going to diagram all of that as kind of just straight lines coming off of the surface of the sky dome. With the idea that all of this light is still reflected light. It's still scattered light. It's not emitted light otherwise I would have a curved surface here but I don't. I've got just a straight line showing that basically this is all reflected light. And so this is a diffuse reflected light source for our solar panel just as the ground is a diffuse reflected light source as well. All of these together are shortwave component sources of light for our solar energy conversion system. Now the ground and the solar panel are each going to also have their own thermal characteristics. Everything glows, right? This is one of the principles of light is that ultimately everything is going to glow. And it's all going to have some light characteristic to it. In our case it's going to be the ground and the panels emitting longwave light. So these guys are emitting longwave light upward into the atmosphere. The atmosphere itself has a temperature. It has an ambient temperature. All those gases have a temperature and so those gases are going to emit as well both down to the ground and up out into space. And so we have actually pretty well diagrammed a lot of the major energy balances of light just using the simple notation. You can see that the temperature of the ground is going to be one source of longwave. The temperature of the solar energy conversion system is going to be another source. The temperature of the atmosphere is another source and of course the temperature of the sun is the source of our shortwave light. And we know the sun is approximated by a black body at about 5777 Kelvin. Whereas all of our terrestrial surfaces are going to be somewhere in the order of 300 Kelvin, much, much lower than the temperature of the sun. And yet we can see that we have a great way to do some quick diagramming to hopefully understand-