 So this is the problem where we're going to be using the de Broglie equation. So it says a rifle bullet with a mass 1.50 grams has a velocity of 7.00 times 10 squared miles per hour. What is the wavelength associated with this bullet? So you have to remember the de Broglie equation in order to do this. So wavelength equals Planck's constant over mass times the speed or velocity of the particular object that you're looking at. So like we were saying, even things that are enormous like this bullet or person, they also have a wavelength associated with them. So that's what we're going to calculate right now. So the thing you want to remember, of course, is Planck's constant is in units of joules, seconds. And if you remember one joule, you guys should all remember this, right, is 1 kilogram meters squared per second squared. And if you don't remember that, you remember it met, because you're definitely going to have to do this. Okay, so what does that mean? That means that miles per hour is not what we want these units in, right? We want them in meters per second. And grams is not what we want these units in. We want it in kilograms. Is everybody okay with me saying that and realizing that, right? Why? Because we're going to want to cancel these units out, right? So we're going to hopefully, since we're looking for wavelength, we're hopefully going to get a length unit, okay? So the length unit I would be hoping to get would be something like meters, right? So let's just plug things in. Well, we've got to convert and then plug things in. So the first thing we're going to do, or the first thing I'm going to do is convert this. So 1,000 grams per 1 kilogram. And this is miles per hour. Okay, just how it was written in the problem. But let's write it kind of more chemistry-like, right? So miles per 1. So if you don't remember, there's 3,600 seconds in an hour. But we can, we'll do it the long way, okay? So we all know that in one hour, there's 60 minutes. So that's going to give us 18 seconds. So that's good. But we want to get our miles to meters, right? So we've got a conversion factor given to us that one mile equals 1.609 kilometers. It's not what we want. We want to do meters so we can cancel out those units. So let's keep going. One kilometer is 1,000. That should give us meters per second, right? So that's a good velocity. It's 760. And I get, so this is the 3,600. I'm going to keep it to a few more 6,600 for right now and then just take the final answer to 3,600. I'm going to erase this conversion here. So I can pass onstand 0.626 times 10 to the negative 34 joules. What do we say joules was? It's kilograms meters squared per second squared, right? So I'm going to put that instead of joules. So kilograms meters squared per one second squared, right? But it's joules seconds, right? So we've got to also multiply the numerator by seconds. So Planck's constant is in units of joules seconds. Don't let it bring you up. So when we do that, we cancel out our seconds there. So now we've got one over mass. So let's just multiply it out like we normally want to. So what's our mass? 1.50. So that's going to cancel there. And then we've got our velocity of one over the velocity. So that's just going to be the inverse of what we have here. So one second, 12.5 meters. So if we see, that's going to cancel meter with meter there. And we have seconds here and seconds up there. So that's going to cancel that with that. And if we notice, we only have units of meters left, OK? So meters are good length units, right? So that would be a link that we are a unit that we would be appropriate for this problem, OK? Is everybody OK with what we've done so far? OK, good. So now I'm just going to figure out what the answer is. So you should expect that the wavelength for something so big would be a very small number, OK? So what did we say? It's going to be to three safetys. So I got 1.33. That's the wavelength of this bullet. And that's the reason why you can't see the bullet waving in the air doing its little waves because the wavelength is so tiny. So if you had an even bigger item, right, the wavelengths would be even smaller, OK? But if you have something like an electron, right, the wavelength is huge or a photon that's effectively massive. So again, the reason I said don't freak out is that we only did this conversion from joule seconds to kilograms meter squared seconds per second squared is because the Planck's constant is in joule seconds. So you got to watch out about that. So undergraduate students like to get scared about that problem, OK? So just watch it and you won't have that issue, OK? I'll record another one of these later today.