 Hello, this is example 3.6.1 from page 143 of the Duffy and Beckman text. So this problem is about the sun, which is 5,777 Kelvin black body radiator. We are asked to find the wavelength, or lambda, the wavelength at which the maximum monochromatic emissive power occurs. And this part of the question is solved by Wien's displacement law, which states that the maximum wavelength times the temperature of the black body radiator is equal to 2,897.8 micrometers Kelvin. So divided by T on both sides, therefore lambda max is equal to 2,897.8 divided by 5,777, which is 0.502 micrometers. So that is the wavelength at which maximum power occurs. So building into the second part of the problem, let's just draw what this looks like. This is wavelength and this is power. The distribution of solar energy looks something like that. So what it's saying is that at this point that happens at 0.5 micrometers. So if this is problem A, problem B asks a second question about the same situation. It asks what is the energy fraction from the source that's in the visible frequency range. So we find these fractional values in table 3.6.1a. And what this is asking, the visible frequency range is from 0.38 micrometers up to 0.78 micrometers. So in this graphic, that's given by a range like that, what is going on in between there. So from the table, we want to find what lambda t is. So 0.38 times 5777 gives us 2195, 0.78, temperature of the black body radiator, is 4506. So with both of these numbers, you can now look it up in table 3.6.1a, obtain the fraction of energy from 0 up to that wavelength. So in the case of the first one, it's 10% and in the case of the second one, it's 56% from that table. So therefore, we can figure out our answer of fViz, the visible frequencies, which is simply 56% minus 10% or 46% of total energy that's in a box, so it's clear what we've done. And that's that. So thank you for listening. That's problem 3.6.1.