Hi. In this video, I'm going to be talking about the light microscope. So the light microscope is something we're probably familiar with. You probably used it in either your high school or some intro classes. But essentially, what it does is it uses light to magnify, or it uses light rays and magnification in order to increase the view of some kind of specimen. For us in cell biology, light microscopes are super important because they can visualize transparent cells, which are the majority of cells, and also some cellular compartments. It only has a 10 to 20-micron diameter that it can view, but that's much better than our eyes and even a magnifying glass, so we use it a lot.
Now, when talking about a light microscope, there are certain terms that you should be familiar with. The first is the limit of resolution, and this is going to be the distance that you can tell two objects apart. So two things sitting next to each other, you know, how far apart can they or how close can they be before you start seeing them as one. If we had an object here and an object here, this distance would have to be greater than 0.2µm in order to be able to tell that there are two particles and not just one large one. That's the limit of resolution.
Then we have the resolving power, and this is the ability to see the fine details of the structure. And they go together well because the smaller the resolution, meaning that the smaller this value is, the greater the resolving power is. So light microscopes have been used for a really long time, and they have been altered over the years to create different types of microscopy to increase some type of visualization of the specimen.
The first one we're most familiar with is bright field microscopy, and this is when you shoot light directly through a specimen. The problem with this is that these specimens actually have to be fixed. So they can't be live cells, they actually just have to be, you know, dead and stuck to a slide. And obviously, not everything we do, like, we want to be able to see live cells too. So it's not the ideal thing, but it's good for some visualization.
Then we have phase contrast microscopy. This improves the contrast so that you can tell the difference between, you know, not colors, but sort of shapes and structures. The resolution is very good. We have differential interference microscopy, and both of these are really important for visualizing live cells, which is awesome.
And then there's a special type called fluorescent microscopy, and this uses fluorescence to detect certain proteins or organelles in the cell. There are two types. I'm not really going to go over the difference. Just know that they're here. They're called FRAP and FRET. FRAP studies the movement of proteins, and FRET visualizes two interacting proteins within the cell.
So if you're to look at, you know, just look under our scope, what you would see is something like this. You have this organism here. You can definitely see through it. There's some structures you can see inside, and if you knew what the structures were, you'd be like, "Oh, that's this, that's this." But you can't really be able to tell, you know, very small fine details of the structure. You can get the shape, which is better than we can get with our eye, but generally, more finer details will require something other than a light microscope.
So that's the light microscope. Let's now move on.
