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The Microscope
Before we can get down to the nitty-gritty of cell division and reproduction, we must take a closer look at the tool that allows us to enjoy this tiny world: The microscope!
Let's take a look at a brief history of the microscope, see how our curiosity about little things started, and where it's going!
Let's take a look at a brief history of the microscope, see how our curiosity about little things started, and where it's going!
Just like telescopes allow us to look outward and see the big picture, microscopes make it possible for us to look inward and understand the building blocks of life. Not only can we learn about the biology of different species, we can learn more about ourselves, and also enjoy some amazing images!
To get started with sexual and asexual reproduction at a cellular level, we of course need to use a microscope! Hopefully you remember the proper way to handle a microscope: hold it carefully with two hands, one on the arm and one under the base, never with only one hand. But do you remember the parts of a microscope, and how to use it properly? Let's take a look at the diagram of our microscopes at NWSS!
Parts of a Microscope
On your notes sheet, you will see the definitions of the parts above, but without their names.
Can you answer all of them?
Can you answer all of them?
I'm a hollow tube that holds the eyepiece lens.
I'm the body tube.
I hold the objective lenses and I rotate to use different lenses.
I'm the turret.
We have a power of 4X, 10X or 40X.
We are the objective lens.
We hold the slide in place.
We're the stage clips.
I am under the stage, and control how much light shines through.
I'm the iris or diaphragm.
I provide the light that shines through the slide.
I'm the light source.
I'm the part you look through, and also have a 10X lens.
I'm the ocular lens.
I support the body tube and make a good handle for carrying the microscope.
I'm the arm.
I'm where you put the slide for viewing.
I'm the stage.
I'm the knob you turn to move the stage up and down.
I'm the stage height adjustment.
I find sections that you may wish to observe further.
I'm the coarse adjustment.
I'm the knob that helps you sharpen the tiniest things.
I'm the fine adjustment knob.
I support the weight of the microscope.
I'm the base.
I'm the body tube.
I hold the objective lenses and I rotate to use different lenses.
I'm the turret.
We have a power of 4X, 10X or 40X.
We are the objective lens.
We hold the slide in place.
We're the stage clips.
I am under the stage, and control how much light shines through.
I'm the iris or diaphragm.
I provide the light that shines through the slide.
I'm the light source.
I'm the part you look through, and also have a 10X lens.
I'm the ocular lens.
I support the body tube and make a good handle for carrying the microscope.
I'm the arm.
I'm where you put the slide for viewing.
I'm the stage.
I'm the knob you turn to move the stage up and down.
I'm the stage height adjustment.
I find sections that you may wish to observe further.
I'm the coarse adjustment.
I'm the knob that helps you sharpen the tiniest things.
I'm the fine adjustment knob.
I support the weight of the microscope.
I'm the base.
When speaking of microscopes and their properties, we use several different terms, such as magnification and resolution. They might seem like the same thing, but they are actually very different!
Magnification is how big a microscope can make an object look. For any of you who has tried zooming in on something in your phone, however, you know that making something bigger does not mean you will see it clearly, as the "zoom" function in our phones is limited, and after a certain number, it becomes simply a digital magnification which expands the pixels out. This ends up blurring things, and it's not ideal for a microscope.
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These two microscopes are the same price on Amazon. Which one do you think would have the best image, and why?
Always look for optical magnification of things rather than digital.
Field of View is the size of the area which you can see. In a microscope, this can be measured in micrometres (µm), commonly called microns.
So, when you put a slide under the scope, how much are you actually seeing when you look into the ocular lens?
This will depend on your magnification! As you increase the magnification of the microscope, naturally you will be able to see a smaller area on the slide; we say that the field of view gets smaller.
The smaller the magnification, the more of your slide can be seen; we say that the field of view gets bigger.
A thousand µm equals one mm.
Always look for optical magnification of things rather than digital.
Field of View is the size of the area which you can see. In a microscope, this can be measured in micrometres (µm), commonly called microns.
So, when you put a slide under the scope, how much are you actually seeing when you look into the ocular lens?
This will depend on your magnification! As you increase the magnification of the microscope, naturally you will be able to see a smaller area on the slide; we say that the field of view gets smaller.
The smaller the magnification, the more of your slide can be seen; we say that the field of view gets bigger.
A thousand µm equals one mm.
- At 40x magnification you will be able to see 5mm.
- At 100x magnification you will be able to see 2mm.
- At 400x magnification you will be able to see 0.45mm, or 450 microns.
- At 1000x magnification you will be able to see 0.180mm, or 180 microns.
Besides the magnification and the field of view, we also have to consider the resolution of our microscope.
Resolution or Resolving Power is the ability a microscope has to focus on different objects, showing them as distinct. In other words, this tells us how blurry our microscope is. Many times, microscopes claim to have a magnification of 1000X -- but this means nothing if it looks like a cloud of mush. Cheaper microscopes are blurrier than others and so it is more difficult to see detail.
The last thing we need to consider is depth of field, which is the depth zone of the image that is in focus, crisp and clear. In this category, the digital microscopes win over the optical microscopes by a large margin! A digital microscope, although unable to give the same level of detail and accuracy at higher magnifications, has a better depth of field because it compacts all the layers it sees into one single image.
This is not only seen in microscopes, but cameras as well! In fact, our phones can take such sharp pictures with such excellent depth of field, that we need filters if we want things to look blurry on the background!
Below, the point of a pin at the same magnification, comparing an optical microscope with a digital one.
Resolution or Resolving Power is the ability a microscope has to focus on different objects, showing them as distinct. In other words, this tells us how blurry our microscope is. Many times, microscopes claim to have a magnification of 1000X -- but this means nothing if it looks like a cloud of mush. Cheaper microscopes are blurrier than others and so it is more difficult to see detail.
The last thing we need to consider is depth of field, which is the depth zone of the image that is in focus, crisp and clear. In this category, the digital microscopes win over the optical microscopes by a large margin! A digital microscope, although unable to give the same level of detail and accuracy at higher magnifications, has a better depth of field because it compacts all the layers it sees into one single image.
This is not only seen in microscopes, but cameras as well! In fact, our phones can take such sharp pictures with such excellent depth of field, that we need filters if we want things to look blurry on the background!
Below, the point of a pin at the same magnification, comparing an optical microscope with a digital one.
As you probably noticed, both the spectromicroscope and the scanning probe microscope look at things from a nano scale. One is not better than the other, and often they are needed in combination to solve a determinate problem!
The Scanning Probe Challenge
You are a team of engineers given the challenge of using a pencil probe to “feel” what is inside a box (without seeing the object or objects).
Teams will need 2 sharp pencils, one for each probe's hand.
Teams will need 2 sharp pencils, one for each probe's hand.
- Choose one of your teammates to be the first probe.
- No one may under any circumstance look into the box.
- Put the probe's non-dominant hand holding a pencil through the hole in the box.
- DO NOT USE FINGERS. Probe will use the tip of the pencil to touch the object, creating a mental image of what it looks like.
- Outside the box, probe will sketch with the dominant hand what it feels like from many angles, to get a good sense of the object.
- Each probe has 5 minutes to complete the scan, from the time the hand goes into the box to the time it comes out. Make sure to time your probes. The objective is to gather as much information as possible.
- When everyone had a chance to scan, return the box to Mrs. Jurgensen.
- Everyone shares sketches in their group and tries to figure out what the object may be, and what it may look like.
- Individually, engineers will draw the object in charcoal, trying to add as much light and shadow as possible.
- Finally, let's open the boxes! Do the drawings match?
To consolidate all this learning, let's work on a booklet with all the parts and important things about the microscope!
MICROSCOPE BOOKLET TIME!
Download and print from the top of the page.
Now that we have chewed through a lot of information about microscopes and how to use them, let's do a lab that shows us these things in practice and up close!
LAB 1 - O is for Onion Skin
Every scientist that studies biology has to draw what they see in the microscope. That is a way to see every detail and not miss a thing. What you draw, you understand! We are now going to explore the microscope and draw what we see in order to understand things better.
Enjoy preparing the two slides for magnification, and comparing what you find!
Enjoy preparing the two slides for magnification, and comparing what you find!
Next, we will be learning all about why some cells look so different! Onward to Mitosis and Meiosis!
