Microscopes and How to Use a Light Microscope

Summary

The video script from Amoeba Sisters introduces viewers to the fascinating world of microscopes, focusing on their importance in observing tiny organisms like protists. It explains key concepts such as magnification and resolution, and explores various types of microscopes, including light and electron microscopes. The script also offers a practical guide on using a brightfield light microscope, from preparing a wet mount to adjusting focus and exploring specimens. Tips for safe operation and cleaning are provided, emphasizing the educational value of microscopes in life sciences.

Takeaways

• 🔬 Microscopes are essential tools for observing tiny organisms like protists, which are often unicellular and require magnification to be seen.
• 🌟 Magnification and resolution are key concepts in microscopy; magnification enlarges the image, while resolution determines the clarity and distinguishability of details.
• 💡 Different types of light microscopes exist, such as brightfield, darkfield, and phase-contrast microscopes, each suited for different观察 purposes.
• 🧬 Electron microscopes, like TEMs and SEMs, offer higher magnification and resolution, making them suitable for observing very small specimens like viruses.
• 📚 The script introduces the parts of a typical light microscope, including the light source, condenser lens, diaphragm, stage, objective lens, and eyepiece lens.
• 🔍 The process of preparing a microscope slide, known as a wet mount, is demonstrated, highlighting techniques to avoid air bubbles for clear observation.
• 👁️ The importance of adjusting the light and using both coarse and fine focus knobs for optimal focusing is emphasized.
• 🔧 Proper handling and maintenance of microscopes are discussed, including cleaning lenses with lens paper and safely storing the microscope when not in use.
• 🌿 Microscopes can enhance life science studies by allowing direct observation of phenomena like mitosis, plant responses, and osmosis.
• 🌟 The video concludes by encouraging viewers to explore the microscopic world and stay curious about the science behind it.

Q & A

What is the main purpose of the conversation between Pinky and Petunia in the script?

The main purpose of the conversation is to discuss the presence of protists on the kitchen table and to introduce the concept of using microscopes to observe these tiny organisms.

Why does Pinky have a sample of green water on the kitchen table?

Pinky has a sample of green water on the kitchen table because she was planning to take some drops and put them on a slide for observation under a microscope, but got distracted.

What is the significance of the term 'resolution' in the context of microscopes?

In the context of microscopes, 'resolution' refers to the ability to distinguish between two separate objects. It is important because it determines the clarity and detail of the image, ensuring that closely spaced objects can be seen as distinct entities.

What is the difference between a brightfield light microscope and a darkfield light microscope?

A brightfield light microscope produces a darker image on a light background, while a darkfield light microscope uses a light stop to block most light, resulting in light images on a dark background.

Why might one choose to use a phase-contrast microscope over a brightfield microscope?

One might choose to use a phase-contrast microscope over a brightfield microscope because it can provide more detailed images of living specimens without the need for staining, offering superior detail compared to a typical brightfield microscope.

How do electron microscopes differ from light microscopes in terms of imaging?

Electron microscopes use electron beams instead of light to visualize images, which allows for higher magnification and resolution, making them suitable for observing very small specimens like viruses.

What are the two main types of electron microscopes mentioned in the script, and what are their主要用途?

The two main types of electron microscopes mentioned are Transmission Electron Microscopes (TEMs), which are ideal for visualizing internal structures of specimens, and Scanning Electron Microscopes (SEMs), which are ideal for visualizing the 3D surface of specimens.

How does the total magnification of a compound microscope like the one described in the script work?

The total magnification of a compound microscope is calculated by multiplying the magnification of the objective lens by the magnification of the eyepiece lens. For example, if an objective lens magnifies 4 times and an eyepiece lens magnifies 10 times, the total magnification would be 40 times.

What is a wet mount and why is it used when preparing a microscope slide?

A wet mount is a technique used to prepare a microscope slide by placing a drop of liquid sample, such as water, onto a slide and covering it with a cover slip. It is used to observe live specimens in their natural, hydrated state without killing or altering them.

What are the three additional tips provided about using microscopes at the end of the script?

The three additional tips are: 1) Be careful with glass slides and cover slips to avoid breakage and loss. 2) Be aware of the slide's position when adjusting the stage to prevent crushing it against the objective lens. 3) Clean lenses with lens paper, not regular tissue, to maintain image clarity.

How can microscopes complement life science studies mentioned in the script?

Microscopes can complement life science studies by allowing direct observation of phenomena like mitosis in onion root tips, plant responses in stomata, and osmosis in aquatic plant cells, providing a visual supplement to theoretical learning.

Outlines

00:00

🔬 Introduction to Microscopes and Protists

The script begins with a dialogue about protists found in 'green water' on a kitchen table, leading to an introduction to the world of microscopes. The narrator explains the importance of magnification and resolution in microscopes, with a focus on distinguishing between objects. The concept of resolution is further clarified with an example of a microscope's ability to differentiate between two objects based on their separation. The video then delves into various types of microscopes, including light microscopes like brightfield and darkfield, which use light in different ways to visualize specimens. The script also touches on other specialized light microscopes and their unique applications. Lastly, the narrator discusses electron microscopes, which use electron beams for imaging and are particularly useful for observing very small specimens like viruses.

05:00

🌿 Microscope Operation and Wet Mount Technique

This paragraph details the practical aspects of using a microscope, including the handling and setup of a brightfield light microscope. The narrator describes the function of various parts of the microscope, such as the light source, condenser lens, diaphragm, stage, and lenses. The process of creating a wet mount from a water sample is demonstrated, emphasizing the importance of avoiding air bubbles and correctly placing the cover slip. The script continues with instructions on how to use the microscope's focus knobs for coarse and fine adjustments, as well as stage knobs for lateral movement. The narrator also shares tips for safely using and maintaining the microscope, such as handling glass slides and cover slips with care, being mindful of the slide's position to avoid crushing it, and cleaning lenses with lens paper. The video concludes with suggestions for using microscopes to explore various life science concepts and encourages viewers to stay curious and explore the microscopic world.

Keywords

💡Protists

Protists are a diverse group of eukaryotic organisms that are not animals, plants, or fungi. They can be unicellular or multicellular and are often studied under microscopes due to their microscopic size. In the video, the character is searching for specific types of protists, such as euglena and paramecia, in a water sample placed on the kitchen table.

💡Microscope

A microscope is an optical instrument that allows the observation of small objects and details that are not visible to the naked eye. It is essential for studying protists and other microscopic life forms. The video script describes various types of microscopes and how they are used to magnify and resolve small specimens.

💡Magnification

Magnification in microscopy refers to the increase in apparent size of an object due to the microscope's optical system. It is a key feature that allows the observation of small details. The script discusses how total magnification is calculated by multiplying the magnification of the objective lens by that of the eyepiece lens.

💡Resolution

Resolution in microscopy is the ability to distinguish between two closely spaced objects as separate entities. It is crucial for accurate observation and is determined by the microscope's optical properties. The script mentions that a resolution of 0.2 microns means two objects must be at least this distance apart to be seen as distinct.

💡Light Microscope

A light microscope is a type of microscope that uses visible light and a system of lenses to magnify images of small samples. The video script explains different types of light microscopes, such as brightfield, darkfield, and phase-contrast microscopes, each with specific applications for viewing specimens.

💡Electron Microscope

An electron microscope is a type of microscope that uses a beam of electrons to visualize specimens. It offers much higher magnification and resolution than light microscopes, making it suitable for observing very small objects like viruses. The script distinguishes between transmission electron microscopes (TEMs) and scanning electron microscopes (SEMs) based on their imaging capabilities.

💡Brightfield Microscope

A brightfield microscope is a common type of light microscope that produces an image where the specimen appears darker against a lighter background. It is typically used in classrooms and is described in the script as having a light source, condenser lens, and objective and eyepiece lenses to achieve magnification.

💡Objective Lens

The objective lens in a microscope is the lens closest to the specimen. It is responsible for the initial magnification of the image. The script mentions that different objective lenses provide different levels of magnification, such as 4x, 10x, and 40x, and are crucial for observing specimens at various scales.

💡Coarse Focus and Fine Focus

The coarse focus and fine focus are adjustments on a microscope that control the vertical position of the stage and thus the focus of the image. The coarse focus allows for larger adjustments, while the fine focus provides more precise focusing. The script describes how these knobs are used to achieve a clear image of the specimen.

💡Wet Mount

A wet mount is a technique used in microscopy to prepare a slide with a liquid sample, such as a water sample containing protists. The script describes the process of creating a wet mount, which involves placing a drop of the sample on a slide, covering it with a cover slip, and then observing it under the microscope.

💡Staining

Staining is a technique used in microscopy to enhance the contrast of a specimen by adding color to it. This can make certain features more visible under the microscope. The script briefly mentions that there are techniques to better visualize specimens, such as using different stains, which can improve the observation of cellular structures.

Highlights

Introduction to the importance of microscopes in exploring the microscopic world.

Explanation of the basic terms: Magnification and Resolution, and their relevance in microscopy.

Discussion of different types of light microscopes, including brightfield and darkfield microscopes.

Introduction to electron microscopes, including Transmission Electron Microscopes (TEMs) and Scanning Electron Microscopes (SEMs).

Detailed explanation of a typical brightfield light microscope's components and how they function.

Step-by-step process of setting up a microscope for viewing a specimen, including adjusting the light source and using different objective lenses.

Description of how to prepare a wet mount slide for viewing under a microscope.

Importance of using proper techniques to avoid air bubbles when preparing a slide.

Explanation of the different focus knobs (coarse and fine focus) and their functions in focusing the microscope.

Advice on handling microscope slides and cover slips to avoid breaking or losing them.

Tips on avoiding damage to slides by being mindful of the stage's position when using focus knobs.

Recommendation to clean the microscope lens with lens paper if the image is unclear.

Instructions on how to properly shut down and store a microscope after use.

Mention of advanced techniques like staining and using immersion oil for better visualization of specimens.

Encouragement to use microscopes to explore various biological concepts, such as mitosis, plant responses, and osmosis.

Transcripts

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“Pinky, what is on the kitchen table?”

“Oh, it’s my protists.

I’m hoping to find some euglena, maybe some paramecia.

I took this sample from—” “Stop, I mean, WHY is it on the KITCHEN

table?!”

“Oh, I got distracted.

I was going to take some drops and put it on a slide while I set

up my microscope.”

“Yes, well, please get your green water away from where we eat.”

“Green water?

Don’t be ridiculous, Petunia, there are tons of protists in here.

We just have to find them.”

“Well, I think you’re out of luck.”

“The protists that I’m looking for are unicellular, meaning, they’re made up of

one cell.

And generally, you need a microscope to see them.”

“Huh.

Never used one of those.”

“You’ve…never used a microscope before?”

“No.”

“Well you know what that means?”

“I’m afraid about what that means.”

“We must explore the world of…microscopes!”

First of all, let’s focus on a few terms that are important in order to understand

microscopes.

Magnification is one.

That’s really what most people think of when they

think of a microscope.

And we’re going to talk more about that in a moment.

But another term that is important is resolution---basically, are you able to distinguish between two objects?

This is important as otherwise two objects could actually look like one object, because

you can’t distinguish between them.

So, for example, if a microscope had a resolution of 0.2 microns, that means two objects needs

to be 0.2 microns or more apart in order to see that they are two different objects and

not one.

If you want to understand the physics of how resolution works and how it’s calculated,

we have a great further reading suggestion in the video details.

So let’s talk about some different types of microscopes that all take into account

this need for magnification and resolution in order to see specimens.

First, light microscopes.

If you’re in a classroom, this is likely what you have.

And, as its name would suggest, it uses light in order to see an image.

Brightfield light microscopes tend to be what people are

familiar with- typically producing a darker image on a light background.

With a darkfield light microscope, you have a piece that blocks

the light source, called a light stop.

The idea is that most light has been blocked so

the only light you see is light reflected or refracted from structures within the specimen

that you’re looking at.

So, you tend to see light images on a dark background.

There are many other types of light microscopes too.

We have a great link for further reading suggestions to learn how each of these work,

and some of these are fascinating---some rely on interference, some rely on using a laser…but

the thing to keep in mind is, there are certain times when one of these types of light microscopes

is more ideal than another.

For example, a phase-contrast microscope can give you a very

detailed image of a living specimen without requiring any stain, and the detail it provides

can be far better than the typical brightfield microscope.

So light microscopes use light in some form to see a specimen.

But not all microscopes are light microscopes.

For example, what if we wanted to see a virus?

Viruses are generally very small- typically much smaller than the

average bacterium.

How can we increase magnification and resolution abilities to see them?

That’s where electron microscopes come in.

Electron microscopes use electron beams to visualize

images.

Transmission Electron Microscopes (TEMs) tend to be most ideal for visualizing

structures within a specimen while Scanning Electron Microscopes (SEMs) tend to be most

ideal for visualizing the 3D surface.

Let’s come back to the typical microscope you might see in a classroom, which happens

to be the one that I own.

A brightfield light microscope.

Here is our light source.

Light passes through this, the condenser lens to focus the light

on the specimen.

The level of light can be adjusted by this, the diaphragm.

Our specimen---likely to be on a microscope slide---will be placed

on the stage here.

Light will be reflected, refracted, or absorbed by the specimen.

But we rely on these lenses here---the objective lens and the eyepiece lens---to get our total

magnification.

In fact, this is often referred to as a compound microscope, because it has

two sets of lenses.

You can see that the objective lenses are attached to this revolving nose

piece which allows them to be rotated so you can select a certain one that you want to

use.

With my particular microscope, I have three objective lenses.

A scanning objective lens that magnifies 4 times, the low power

objective lens that magnifies 10 times, and the high power objective lens which magnifies

40 times.

But don’t forget the eyepiece lens because that also magnifies images, and

my particular eyepiece lens magnifies 10 times.

So let’s say I use the scanning objective lens.

I would multiple that objective lens magnification level by the eyepiece lens magnification

level so that my total magnification is 40 times.

Now, you’ll also notice there’s a lot of knobs here.

Let me introduce you to the knobs.

This large knob here is known as the coarse focus and then this smaller knob here

is known as the fine focus.

Both of these knobs raise or lower the stage, which helps

with focusing.

The coarse focus knob will move it more dramatically whereas the fine

focus knob will move it in smaller increments.

These knobs- the stage knobs- don’t move the stage up and down but rather from side

to side instead.

It helps you explore what’s on the slide itself, but it isn’t adjusting

the focus of it.

Not all microscopes have those stage knobs; sometimes you have to move

the slide manually.

This is the microscope arm and the base.

Whenever you pick it up, you want to make sure you

have one hand underneath supporting the base and the other hand holding the microscope

arm.

Since it plugs in, you want to make sure there isn’t water around it.

So, let’s take a look at what’s in this water sample here.

I’m going to do something called a wet mount to prepare my microscope

slide.

I’m going to drop a drop or two of my water sample onto the slide using a disposable

pipette.

It’s like a very fancy eyedropper.

Kind of.

I’m going to put a cover slip on top.

There’s some techniques to doing a wet mount to avoid air bubbles that you can

check out online.

Air bubbles actually can look kind of beautiful under the microscope---which

can lead to great disappointment when you find out they’re not some amazing microscopic

organism but rather just an air bubble--- something I may or may not know by experience.

I’m going to put the slide on the stage.

I’m going to use the stage clips here to secure the slide.

Light is on, and I already have the scanning objective lens here ready

to go, which is good, because I want to find the specimen first.

I can adjust the light level if I want---but just know that super

bright doesn’t always mean the best image.

I can look through the eyepiece and use the coarse focus knob to move the stage up or

down slightly to focus.

Patience.

Euglena!

I can also fine-tune focus it with the fine focus knob.

I can use the stage knobs to center my image.

Now that I found it with the scanning objective lens, I’m now going to move up

to the next magnification level.

So, remember, total magnification would be 100 times.

Since I had already focused it with the scanning objective lens, it’s likely I only need

to use the fine focus knob to adjust the focus at this level.

I could continue to move up to the high power objective lens, which would

give me a total of magnification of 400 times.

Now 3 additional tips about using microscopes that I just want to mention.

1) Most microscope slides are glass so they can break if dropped.

And if using cover slips, keep in mind they are extremely easy to lose

if not careful.

2) Always be aware of where the slide is when you’re moving the stage up and down with

the focus knobs.

It’s possible to move the stage too close to the objective lens and

actually crush the slide.

3) If it’s hard to see your image even when focusing, you may need to clean the lens.

But you need to do this by wiping it with lens paper.

Not regular tissue.

When you’re done with the microscope, make sure the slide is removed, turn off the light,

lower the stage to its lowest position, and return the lowest power objective lens over

the stage.

Unplug it and wrap up the power cord.

And if you have a cover, cover the microscope before putting it away.

Keep in mind there are some techniques to better visualize some specimens such as using

different stains or using immersion oil at high magnification to increase resolution.

Definitely something to explore that this video doesn’t go into.

Microscopes open up an entire world that you can’t see with the naked eye.

Microscopes can also complement what you might be learning

in life science.

Studying mitosis?

Check out the cross section of an onion root tip, where

lots of mitosis happens.

Studying plant responses?

Take a look at stomata from a thin sample underneath a leaf.

Studying osmosis?

Take a look at how aquatic plant cells respond

to different salt concentrations.

Endless possibilities to explore endless curiosity.

Well that’s it for the Amoeba Sisters, and we remind you to stay curious.