In this video we're going to look at microscopy, which just refers to the use of microscopes. So we'll cover how light microscopes work, and then explain what the terms object, image, magnification, and resolution mean. Let's start though by looking at the different parts of a light microscope.
Supporting the entire thing is the base at the bottom, and then the arm that connects the bottom to the top. Then we have some kind of light source, which on some microscopes will be a lamp, but in this case it's just a mirror that will reflect the light from the room. And just above it is the stage, which is where we put our microscript slide.
Then in the top half we have all of our lenses. So we normally have three objective lenses, which we can choose between, and each have different magnifications, like perhaps 10 times, 20 times, and 50 times magnifications. and then we also have an eyepiece lens which has a fixed magnification and sits at the top where we look into the microscope. Then the last things to notice are the body tube just here and finally the coarse and fine focusing knobs which we can turn to help us get the image in focus.
Now before we go any further we need to introduce the terms object and image. In microscopy the term object refers to the real object or sample that you're looking at. So if we had some onion cells on our microscope slide, then the onion cells themselves would be the object. The term image on the other hand refers to the image that we see when we look down the microscope. For example, if we were to look down this microscope, we might see something like this.
So this would be our image of the onion cells, whereas the object is the actual onion cells that are sitting there on the microscope slide. So, just be really careful not to get these two terms confused. If we move on to how they work, light from the room is going to hit this mirror here, and be reflected upwards through the object that we want to look at.
In this case, through our onion cells, which remember are sitting there on the stage. Then it'll pass through one of the objective lenses, then through the eyepiece lens, and finally into our eye, which will be looking into the eyepiece. And the idea of this whole thing is that the lenses will spread out the light rays, so that the image that we see is far larger than the actual object. This brings us nicely to our next term you need to know, magnification, which we can define as how many times larger the image is than the object. So if the image appeared 1000 times larger than the object, then the magnification would be times 1000. There's also an equation for magnification which says that magnification is equal to image size divided by object size, and we're going to take a look at how to use it in another video.
The final term you need to know is resolution, which we can define as the shortest distance between two points on an object that can still be distinguished as two separate entities. Now, I know that this is kind of a complicated definition, but it basically means the shortest distance that two parts of an object can be apart without a pairing blurred. Or in other words, it's a measure of how detailed the image is.
For example, if we look at these two images of the onion cells from earlier, we can see that they both have the same magnification. because they both have times 100 in the bottom corner, and the cells in each image both look the same size. However the one on the right looks much blurrier, and this is because it has a lower resolution, so we can't see the same level of detail.
So in general just remember that the higher the resolution of an image, the more details you'll be able to see, and the less blurry it will look. Anyway... that's everything for this video. So if you want to practice questions on this then just check out the link in the top right corner of this screen or in the pinned comment down below and hopefully we'll see you next time.