Y10: Microscope Revision

• Science
• Lower Secondary (Key Stage 3)

Y10: Microscope Revision

Cell membrane

Cell wall

Nucleus

Vacuole

Cytoplasm

Chloroplast

Mitochondria

Ribosome

Structure

Function

Controls what enters and leaves the cell.

Contains DNA and controls the cell processes.

The site of respiration.

The site of chemical reactions in the cell.

Storing cell sap and keeping the cell rigid.

The site of photosynthesis. Contains chlorophyll.

Protects and supports the cell.

Protein synthesis (making proteins).

Cell membrane

Chloroplast

Cell wall

Vacuole

Mitochondria

Nucleus

Cytoplasm

Ribosome

Follow the link to a virtual microscope:

https://www.ncbionetwork.org/iet/microscope/

Spend some time exploring the different parts of the microscope. How does each part work and what is its function (job)? If you were going to look at a slide under the microscope, what order would you do things?

Click on each hotspot to learn more.

Eye Piece Lens

The eye piece lens is the part of the microscope that you look through to see the image. It usually has a low magnification (x10).

Objective Lens

There are 3 objective lenses, each with a different strength of magnification. Combined with the eye piece lens they will make the image many times bigger than its actual size. When using them, we always start on the lowest powered lens and rotate through to the highest power.

Stage

This is the flat section of the microscope that we will place the slide on. There are clips to hold the slide in place. Always start with the stage lowered as far from the objective lens as possible.

Coarse Focus Wheel

Turning the coarse focus wheel moves the stage closer/further from the objective lens. When looking at a slide, start with the stage lowered and then turn the coarse focus wheel until an image appears/comes into focus when looking through the eye piece lens.

Fine Focus Wheel

The fine focus wheel is used to make small adjustments to the clarity of an image. Once you have used the coarse focus wheel to bring the image into view, carefully turn the fine focus until the image is perfectly clear. 

We use microscopes to magnify small objects that we cannot see with the naked eye.

You need to know the different parts of a microscope and how to use one correctly.

Label the microscope.

Objective lens

Fine focus wheel

Coarse focus wheel

Eye piece lens

Stage

Light

Which part of the microscope is missing?

1. Objective Lens
2. Eye Piece Lens
3. Coarse Focus Wheel
4. Fine Focus Wheel

Which part of the microscope is missing?

1. Objective Lens
2. Eye Piece Lens
3. Coarse Focus Wheel
4. Fine Focus Wheel

Which 2 parts of the microscope magnify an image?

1. Objective Lens
2. Eye Piece Lens
3. Coarse Focus Wheel
4. Fine Focus Wheel

Match the part of the microscope to its function.

The part that you look through. Magnifies the image at a low power.

Magnifies the image, starting from the lowest power and moving higher.

The platform the slide is placed on.

Moves the platform up and down to bring the slide into focus.

Makes small adjustments so that the image is completely clear.

Stage

Objective lens

Coarse focus

Fine focus

Eye piece lens

What problem might you have if the fine focus wheel was broken?

A student's microscope image looks like this. What could they do to make it clearer?

A student's microscope image looks like this. What could they do to make it clearer?

To get a clear view of an image, you must follow the steps of using a microscope in the correct order:

Put the steps for viewing an image in the correct order.

Place the object you wish to observe on the stage.

Select the objective lens with the lowest magnification and look through the eyepiece.

Turn the fine focus knob until the object comes into focus.

Turn the coarse focus knob until you can see your object.

Move the stage to its lowest position.

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 2

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A student has a leaf that they would like to look at under a microscope. Write a step-by-step method to help the student get a clear, magnified picture of their leaf.

It is useful to know how many times bigger the image that we are looking at is compared to its actual size.

There are 2 ways to calculate the magnification, depending on what information you have.

These equations will not be given to you in your exams. You will need to learn them by heart.

1. If you know the power of the eye piece lens and the objective lens:

Total magnification = Eye piece lens x Objective lens

e.g. if the eyepiece is x10 and the objective is x40

Total magnification = 10 x 40

                                      = x400

Calculate the total magnification when the eyepiece lens is x20 and the objective lens is x100

Calculate the total magnification when the eyepiece lens is x10 and the objective lens is x50

Calculate the total magnification when the eyepiece lens is x10 and the objective lens is x20

Test yourself: can you get 100% on challenge mode?

Light microscopes vs. Electron microscopes

1. If you know the size of the image and the size of the actual object.

Total magnification = Image size  ÷  Actual size

e.g. if the image is 500mm and the object is 25mm

Total magnification = 500  ÷  25

                                      = x20

Calculate the total magnification when the image is 250mm and the object is 25 mm

Calculate the total magnification when the image is 2600mm and the object is 130mm

Sometimes the image size and actual size will be given in different units. Before you can calculate magnification, both must be converted to the same unit e.g. millimetres.

To convert from micrometres to millimetres, multiply by 1000.

1 mm =

1. 10μm
2. 100μm
3. 1000μm
4. 0.1μm

27 mm =

1. 270μm
2. 2700μm
3. 27000μm
4. 0.27μm

Convert 0.5 mm into μm.

Convert 0.017 mm into μm.

Convert 300 μm into mm.

Convert 2400 μm into mm.

Calculate the magnification if the image of a cell is 14mm, but its actual size is 42μm

Calculate the magnification if the image of a cell is 3.6mm, but its actual size is 9μm

Calculate the magnification if the image of a cell is 2.4cm, but its actual size is 0.06mm