 So this one says an absorption in an electronic spectrum is recorded at 17,000 wave numbers. So remember, wave numbers is centimeters to the minus one. What does this correspond to in nanometers? So that's a wavelength, wave numbers, and nanometers is also a wavelength. So let's convert this to nanometers. So how do we do this? The first thing you want to remember is kind of the units here giving you a clue, okay? So it's saying that this is in wave numbers. So it's something like this. You want to write it down. 17,000 divided by one centimeter. That's what it's saying, okay? Because the minus one, that's under the denominator, right? So what we want to do is get this in nanometers, right? So we're going to flip that thing over because we want to put it in centimeters to start out with it. So in other words, we have 17,000 on the bottom and one centimeter on the top. When we do that, I'm going to go up to meters and then back down to nanometers, okay? So 100 centimeters is one meter like that and then what do we have? One meter is one times ten to the nine nanometers like that, okay? So cancel, cancel, cancel, cancel. So wave numbers to nanometers, this is how you do it, okay? So now all we do is plug and chug because our units here are what? Nanometers, right? So we've got the units, everyone. So ten to the ninth divided by 100 divided by 17,000 and I get... So two significant figures, okay? So remember this is two significant figures because it says 588 in the answer but it's two significant figures, it's going to be 590 nanometers. So if you've got a band that comes at 17,000 wave numbers, it's going to be coming at a wave length of 590 nanometers. So if there's a question, ask before the thing turns off.