Lesson video

- Hi there.

My name's Mrs. Buckle and I am going to be helping you through today's science lesson.

So welcome to today's science lesson with Oak.

You are going to need some way to write down your ideas so a pen and paper or a digital device.

And you're also going to need a calculator for the last part of our lesson today.

So without any more hesitation, let's get started.

This title is Microscopes and this is the first lesson within the science cells unit of Key Stage three at Oak.

And what we're gonna be doing today is learning about microscopes.

We're gonna label and describe how to use the microscope as well as how to use a microscope to calculate magnification.

Before we get started, I just want to look over some of the keywords that will be popping up here and there throughout the lesson so that we're prepared for them when they do arrive.

The first word is specimen.

A specimen is just anything that is looked at using a microscope.

It could be a sample, so a small piece of something, it could be an organism, it could be a non-living thing, it could be a larger thing that we want to see in more detail.

Anything that's for you to use a microscope is a specimen.

Our second keyword today is magnification.

Magnification is how much an object has been magnified.

So by how much of a factor have we zoomed in an object to look at it, that is magnification.

And finally a micrograph is an image produced when using a microscope.

So just like a photograph is an image produced using light, a micrograph is an image produced using a microscope.

So there's are keywords today.

Let's look at what we are going to be learning.

So we are gonna start by labelling the parts of a microscope.

Then we're gonna describe how to use one.

And finally, we are going to use the information from a microscope to calculate magnification.

Let's get started by labelling the parts of a microscope.

So this is a microscope.

A microscope is a piece of equipment that is used to view very small objects or smaller objects in more detail.

And one of the many uses of a microscope is that we use it in science to look at cells.

Now we need to have a think, what other things could be viewed using a microscope? Write out some ideas and pause the video.

Come back when you are ready to continue.

Alright, welcome back.

You might have come up with ideas such as really, really small things like tadpoles or seeds or pollen.

You might have thought of non-living things such as things like thread or pieces of paper or bits of metal.

Could be anything that is really, really small or anything that has very fine detail that we might not be able to see just regularly with our eyes.

A microscope is made of lots of different parts and each part has a different function, a different job.

We are going to look at each part of the microscope and just have a look at what it does.

So we're gonna start over on the right hand side of the image and we're gonna look at these two wheels here.

The larger wheel is called a coarse focus and the smaller wheel is called a fine focus.

These can be turned and they help us to focus the image so make the image a bit clearer.

The coarse focus focuses in larger increments and the fine focus uses smaller increments.

They're normally found at the top of the microscope but they can be found at the bottom.

But both of these wheels are found on this part of the microscope, which is called the arm.

The arm is the large curved piece of a microscope and it's usually used to help us to carry the microscope around and it's curved so we can get a nice solid grip on it, so we're not gonna drop it or damage the microscope in any way if we're transporting it around a lab or around an ecosystem to look at different things.

We've also got these stage clips.

These are just like clips in your hair or paper clips and they help keep things in place and I'll come back to those in a little second.

At the bottom of the microscope we have got a light source.

On modern microscopes, these tend to be a bulb that you turn on and off so it actually shines light from the bulb straight up through the microscope.

Older microscopes have a mirror and you can adjust the angle of the mirror so that it feeds light from your surroundings up through that structure at the bottom and all the way through the specimen.

The specimen is found on the stage and this is just a flat piece of plastic or metal just above the light source.

And we can see that the stage clips attach to the back of the stage and the stage clips help keep what we are viewing in place so that it doesn't slide off or get damaged or move positions as we're viewing it through the microscope.

Above the stage we have objective lenses and the objective lenses are on a wheel that rotates.

You've normally got three objective lenses on a microscope but some have fewer, some have more.

Each objective lens gives us a different factor of magnification, so some have a higher magnification than others and you twist them and keep them in place above the stage and that helps magnify the image.

And finally at the top we've got the eyepiece lens.

Eyepiece lens is a piece of glass in a tube and we look through the eyepiece lens to view our image.

The eyepiece lens we can see is connected to the objective lens via tube and both of those lenses work together to magnify the specimen that you are viewing.

So those are the parts of the microscope.

We're gonna have a bit of a practise now with some check for understanding and tasks.

Let's have a look at the first one.

So for each check for understanding task, I will read out the question.

Then I want you to pause the video and choose your answer and come back to me when you are ready to check if it's correct.

In each of these check for understanding tasks, we are looking at the arrow on the image and I would like you to tell me which part of the microscope the arrow is pointing to.

So for the first one, which part of the microscope is the arrow pointing to here? Well done if you said eyepiece lens right at the top of the microscope, we have the eyepiece lens.

Which part of the microscope is the arrow pointing to this time? Well done if you said the arm of the microscope, remember the arm, of the microscope is also in curved.

We are able to carry the microscope around.

Which part of the microscope is the arrow pointing to now? Well done if you said objective lens, the objective lenses are found on this wheel that can be rotated for us to choose the correct objective lens.

Which part of the microscope is the arrow pointing to here? Well done if you said light source, remember the light source could either be an electrical light are such as a bulb, that is turned on or off, or it could be a mirror at the bottom of the microscope.

Which part of a microscope is the arrow pointing to here? Well done if you set the stage, the stage is found just above that light source and is a flat structure within the microscope.

Okay, for task one of today's lesson, I would like you to use this photograph of a microscope and thinking about all the parts of a microscope that we've just looked at on our diagram, I want you to take the words at the bottom of the image and add them into the correct box and label the key parts of a microscope.

Take your time with this.

Come back to me when you are ready to check your ideas and we'll pause the video here.

Okay, welcome back.

Let's check these ideas.

I'm gonna start on the right hand side of the image and work my way around.

So at the top we should have got eyepiece lens, underneath that the objective lenses and there's more than once, so it's plural.

Underneath that we had the stage and right there at the bottom is the light source.

In this example of a microscope the light source is a mirror, but remember it could also be a bulb.

Around to the other side then above the light source we have got the stage clips and then the arm, the fine focus is the smaller of our two wheels, and the coarse focus is the larger of those wheels.

Make sure you've ticked or corrected all of your answers and well done at getting those labels down.

Okay so, so far today we have labelled the parts of the microscope.

Now we are going to describe how to use a microscope.

So to describe how to use the microscope we are going to work through our method.

A method in science is a set of instructions that allows a scientist to carry out a particular investigation or experiment.

And there are normally numbered sets that are really concise and clear and tell the scientist what to do.

To use a microscope there are a few different steps and we have some new equipment too.

First of all, we're gonna start with our microscope and we are going to adjust the light source.

This could be turning on the bulb or it might be adjusting the angle of the mirror.

And how I'm gonna do that is I'm gonna keep looking down the eyepiece lens and checking to see if I can see light.

If the light source isn't quite right all I'll be able to see is pitch black when I look down the eyepiece lens.

Then I'm going to take a slide and add the specimen onto the stage.

This is then held in place using the stage clips.

So let's have a look at this.

A slide is a small piece of glass, normally rectangular in shape, and the specimen is placed in the middle of that slide.

You can get slides that are pre-made, so already have the specimens put on there for you by another scientist, but you could also make your own slide by adding a specimen onto the glass.

The slide is then placed onto the stage so it looks like this and the stage clips hold it in place.

That's really important for two reasons.

We want the specimen to stay above that light source so we can see in as much detail as possible.

But also our slide is made of glass and the stage clips stop it from falling off the microscope and potentially smashing.

So it's good for viewing our specimen but also for health and safety reasons.

Once our specimen is on the microscope then we are going to look at the magnification power.

So step three in our method is to use the lowest magnification objective lens to focus on the specimen.

We can see here an image of a microscope.

This microscope has four objective lenses and we can see that on each objective lens there are a series of numbers.

The number tells us the magnification power.

So when we first look at our specimen we are going to use the lowest magnification power so the objective lens with the smallest number on and would rotate that until it clicks in place above the specimen.

You can see here that the yellow objective lens is clicked in place to view the specimen.

Then we would look down the eyepiece lens and check that we can see everything.

And once we've been able to see something we can then later on rotate those objective lenses to use a higher magnification and we would refocus the microscope using the fine and coarse focus wheels.

The fine focus wheel is used right at the end because that's the smaller details that we want to see.

And again, we do that just by turning the wheel really, really slowly and it'll adjust the focus of the image that we are seeing.

Let's have a go at quick check for understanding question then.

What is the name of the piece of glass which holds the specimen? Well done if you said slide, the stage is where the slide is placed.

And then microscope is the piece of equipment that we use to look at cells but slide is the name of the piece of glassware.

Which piece of the microscope needs to be turned to make the image clearer? Well done if you said the focus wheels, now remember there are two focus wheels, the fine focus and the coarse focus.

Which piece of the microscope can adjust the magnification? Well done if you said the objective lenses.

Remember the focus wheels are only there to adjust the clarity or the the clearness of the image.

Okay, so once we set up our microscope we can look down our eyepiece lens and see our specimen.

The image that we're seeing is called a micrograph.

Now underneath my text there are three images.

Each one is a different micrograph, I've got some in colour and some in black and white.

I want you to have a think about what these micrographs might be showing.

Remember they're going to be something that's really small or something larger in much more detail.

Pause the video, write down your ideas and come back to me when you are ready to find out the answers.

Okay, welcome back.

Let's see if you are right.

The first one is possibly the trickiest one.

That is actually a leaf so it's the bottom of the leaf and you can see it's got all these hairlike projections.

That's what makes the bottom of the leaf feel nice and soft and smooth.

The second one is a mite, which is a type of microscopic insect.

You can have dust mites, carpet mites.

There are lots of different types of mites.

They're very, very small.

This is a mite that's actually on a piece of furniture.

We can see all the fibres behind it and the mite is super, super small within that structure.

And last one, this one's my favourite.

This is an ice crystal.

This is actually on the top of ice cream and we can see that each ice crystal is different and it's 3D and it's actually quite rough.

Okay, so that is an ice crystal.

All three of those images are examples of micrographs which is an image that is seen through in microscope.

A quick check for understanding question then, what is this image showing? Well done if you said ice.

This is actually from a snowflake so we can see all the ice crystals behind it.

And then there's the one ice crystal or snowflake in focus at the front.

Okay, then for task two, what I would like you to do today is first of all create a method.

So there are a number of statements that need putting in the correct order.

One and two have been done for you.

So you can see all you need to do is do three, four, five, and six and write the numbers next to the step in the method which you think comes next.

And then for question B, I would like you to name the image produced when you're using a microscope.

Take your time with this, make sure you're happy with your answers before you come back to me and then we'll go through the correct answers.

Okay, let's have a look at these answers then.

Step three was move the stage clips down and hold the slide in place.

Step four, rotate the objective lens to select the one with the lowest magnification.

Step five, look down the eyepiece so you can actually see the image.

And step six, turn those focus wheels, the coarse and the fine focus, to make the image clear.

And then finally at the bottom, the type of image you produced when using a microscope is a micrograph.

Okay, so we have labelled the parts on the microscope.

We have described how to use a microscope.

That takes us to our final objective for today which is calculating magnification.

We're gonna come away from the microscope for a second and we're gonna look at this image.

This is Times Square in New York.

We can see it's really, really busy.

There's lots of adverts and really tall buildings.

Can you read the time on the clock? I've put a box around the clock.

You might be able to see it if your eyesight's very good.

What do you think it might be? Okay, can you read the clock now? Hopefully it's much, much easier for you to see that the time on the clock is 10:57.

It's easier to see because the image that we had has been magnified.

I have zoomed into a particular part of the image so I can see it in more detail.

Smaller details and structures can be seen when a microscope is used and that's because we are magnifying those structures and details using the lenses in a microscope.

So if I have this leaf and I'm magnify it, I can now see the cells within the leaf, which are much much smaller structures that I wouldn't be able to have seen with just my eye.

So let's have a look at some more micrographs.

I've got this micrograph at a times 10 magnification.

This micrograph at times 100 magnification and this micrograph at times 200 magnification.

Have a think.

What is different about each of these micrographs? Come back to me when you're ready to share your ideas.

Okay, hopefully we've been able to see that in each micrograph I can see more detail.

At the times 10 magnification I couldn't see these sort of fabric type structures within the cells and at times 100 magnification I couldn't really see what was inside of each of the cells which I can do kind of in times 200.

I can see that within each cell there are smaller, circular structures.

Each magnification power allows me to see smaller details in more clarity.

To calculate the total magnification power of a microscope we use the following equation.

The total magnification of the microscope is equal to the eyepiece magnification multiplied by the objective lens magnification.

So each of these lenses has a magnification power and on the microscope itself, we would actually find numbers and I've just made them a little bit bigger so we can see them on these images that tells the magnification power.

So for example, on this microscope the eyepiece lens is times 10 which means it magnifies the image on its own 10 times bigger.

And the objective lens magnification here is times 40, which means that that lens magnifies the image 40 times bigger.

So the total magnification here would be 10 multiplied by 40, which would be 400.

Let's have a go at some check for understanding tasks.

How can the total magnification of a microscope be found? Well done if you said we multiply the eyepiece magnification and objective lens magnification.

Okay, I'm gonna show you a work example now and in a second you're going to have go at one on your own.

The question says, calculate the total magnification power of a microscope when using an eyepiece lens magnification of times 10 and an objective lens magnification of times 40.

The first thing I would do is write out the equation I'm going to use and that is total magnification is equal to eyepiece magnification multiplied by objective lens magnification.

I would then substitute my numbers so I know the eyepiece magnification is 10 and I'm going to multiply that by the objective lens magnification, which is 40.

I pop that on my calculator and I get a total magnification of times 400.

The multiplication symbol goes in front of our number and that is the unit for magnification.

You have a going now.

Calculate total magnification power of a microscope when using an eyepiece lens magnification of times 20 and an objective lens magnification of times 100.

Have a go at this and come back to me when you're ready to check your answer.

Well done If you said times 2000.

I got that answer by doing 20 multiplied by 100.

For task three today you are going to have a go at these questions which summarise how we calculate magnification.

Which two values are multiplied together to calculate the total magnification of the microscope? Describe where the magnification values can be found on the microscope.

And calculate the total magnification power of a microscope within eyepiece magnification of times 10 and an objective lens magnification of times 20.

Once you've finished all three of these questions, resume the video, and I will give you the answers to check your work.

Okay, here are the answers.

The two values that we multiply together are the eyepiece lens magnification and objective lens magnification.

Where the values can be found, they are written on the eyepiece lens and objective lenses.

And if we had an eyepiece lens of times 10 and are objective lens of times 20, the total magnification would be timed 200.

So to summarise our learning today, a microscope is a piece of equipment that is used to view very small objects.

The image created is called a micrograph.

Objects can be viewed on a microscope by placing a slide containing a specimen on the stage and using stage clips to hold it in place.

Starting with the smallest objective lens magnification, look down the eye piece and adjust the light source if you need to.

And then we turn the focus wheels to make the image clearer.

The total magnification power of a microscope can be calculated by using the following equation, Total magnification is equal to eyepiece magnification multiplied by objective lens magnification.

The last thing for you to do today is an exit quiz and the link is on the slides.

You have done fantastically today.

I hope you have enjoyed learning all about microscopes and how we use them, and I look forward to seeing you very soon for some more science lessons.

Have a great day.