Transcription
So we've looked at the strong force. Let's move our attention now to the weak force, and I'm going to show you how this force works by way of an example.
Now, the weak force is a complex force, and there are multiple different interactions, many of which we will cover in our nuclear medicine module. But here, I'm going to show you how we can change a neutron into a proton by way of the weak force, and this is what's known as beta minus decay, a really important force when it comes to radiology physics.
So again, we've seen the subatomic particle overview. Our hadrons are here. We're changing a neutron into a proton, and we're going to use the force carriers of the weak force, the W and Z bosons. So let's see how this weak force works.
Now, much like the strong force, the weak force only works over very small distances, distances in the level of atomic and subatomic particle distances. The electromagnetic force and gravity, those can work over small distances as well as over kilometers and the scale of the universe. Here, the weak and the strong force act over very small distances.
So we've said our force carriers here are the W and Z bosons. Now, we've seen this is an electron neutrino here attached to a W boson, and they interact with the down quark of our neutron. Now, when we looked at the strong force, I showed you how the gluon changed the property of the quark known as color. Here, the W boson is also going to change a property of the quark, but not color, or charge, or mass, or spin. It's going to change the quark type.
And now, this is how we're able to change a neutron into a proton. This W boson changes the down quark into an up quark, and that process not only changes a neutron into a proton but also releases an electron. This is what's known as beta minus decay.
Now, you'll see if this is in an element, not only have we changed the neutron into a proton, but we've actually changed the element itself, because the number of protons within an element determines which element that is. So we've effectively lost a neutron and we've gained a proton. Our mass number has remained the same, but our atomic number has increased by one.
Now, this is just one of many examples of the weak force, and you can see how powerful the weak force is. We have the ability to completely change an element. Now, the weak force, for me, is the most interesting and most complex of the fundamental forces, and I've spent a lot of time going down a major rabbit hole seeing how the weak force actually only interacts with specific particles in specific orientations. And if you've got time in your studying and you're not cramming last minute, I'm going to leave a couple of links in the description for you to pursue if you feel so inclined, but nothing more than this is going to come up in your radiology physics exams.
Now, as I've mentioned, I've curated a question bank from over 10 years of past papers from countries all over the world and ranked those questions in order of frequency that they come up in exams. So if you are someone that's cramming, you don't have time to go through and read all these articles that I've linked about the weak force, then I'd highly recommend going through that course.
So our next talk, we're going to look at the last of the fundamental forces in this course, and that's perhaps the most important, the electromagnetic force, which we use in every single module throughout this physics course. So I'll see you all there. Goodbye.