Biological Principles: Microscopes Recall the names of the parts of a microscope Successfully use a microscope to make a biological drawing Calculate magnifications Correctly use size prefixes mili, micro, nano and pico

4. How do you work out the magnification of your microscope? 1. Can you label the parts of the microscope? 2. Why is this called a light microscope? 3. How does a light microscope work?

4. How do you work out the magnification of your microscope? 1. Can you label the parts of the microscope? Eyepiece lens Multiply the magnification of the eyepiece lens (usually 10) by the magnification of the objective lens. Arm Objective lens Stage Focussing wheel 3. How does a light microscope work? Slide with specimen Light source Light passes through the specimen. The Objective and eyepeice lenses magnify the image. The focusing wheel helps focus the image on our retina. 2. Why is this called a light microscope? Light is passed through the specimen into our eyes

How to use a microscope Use the focusing wheel to wind the stage all the way down. Add your specimen on the slide, over the light source Turn the objective lens to the lowest power (the smallest / shortest lens) Use the focusing wheel to wind the stage up. Look through the eyepiece lens. The image should appear when the stage is close to the top. Use the focusing wheel to slowly bring the image into focus Now you can change to a higher powered objective lens to get a greater magnification.

What can I see? You might have a pointer in your eyepiece lens You might have an eyepiece graticule – a mini ruler

Biological Drawings When drawing something down a microscope: Always use pencil Use thin, un-feathered lines Do not shade. Make your diagram large – fill the space. Label the structures you can identify using a ruler Write the name of the specimen and the magnification viewed on (objective lens x eyepiece lens).

How big is it? milli- pico- nano- kilo- micro- Microscopes magnify objects to make them seem bigger than they are, but how big are they? Very small objects need very small measurements, so what units do we use? What are these terms used for? Which is the largest? Can you put them in size order? What do they mean? milli- pico- nano- kilo- micro-

Kilo means one thousand. Milli means one thousandth Micro means one millionth Nano means on billionth Pico means one trillionth To convert between each of these units you need to divide or multiply by 1000

Magnification and Resolution Magnification is how many times the image has been enlarged. It is calculated by multiplying the magnification of the eyepiece lens by the magnification of the objective lens. Our school microscopes have an eyepeice lens with x10 magnification. The objective lenses have x4, x10 and x 40. What total magnifications do the microscopes have?

Look at the two pictures of the van. What will happen if we zoom in on (magnify) the number plate in each picture? Why?

Its all about Resolution! Resolution is how clearly the image can be seen. It refers to how close two objects can be to each other and still be seen as being separate.

Resolution The detail that can be seen with a microscope (or a camera) depends on its resolution This is the smallest distance between two points that can still be seen as two points. Microscopes have improved considerably since they were first invented! Hooke’s microscope 1665 X30 magnification 0.002mm resolution Van Leeuwenhoek microscope - 1675 X270 magnification 0.0014mm resolution Modern light microscope - 2016 X1500 magnification 0.0001mm resolution Modern electron microscope - 2016 X2000000 mag 0.2nm resolution

Electron Microscopes Electron microscopes fire a beam of electrons through the specimen, and a camera detects where they end up. For an electron microscope to work the specimen must be put into a vacuum – therefore it must be dead. Electron microscopes have enabled us to learn far more about cells because they have a greater magnification and a much higher resolution. We can now see structures inside cells far more clearly.

Electron Microscope images

Microscopes Quick Quiz © Pearson Education Ltd 2015. Copying permitted for purchasing institution only.

Quick Quiz 1 What does a microscope do? makes small objects appear larger/magnifies small objects 2 What part of a microscope do you look through? eyepiece lens 3 Which part of a microscope do you use to get a clear image? the focusing wheel © Pearson Education Ltd 2015. Copying permitted for purchasing institution only.

Quick Quiz 4 If an average height person in Year 10 is magnified 600 times, how tall will they be compared to the tallest building in the world, which is 828 m tall? about the same height; the Burj Khalifa, Dubai is 828 m tall Put these in order of size, biggest first: atom, animal cell, cell nucleus, muscle tissue, protein molecule, water molecule muscle tissue, animal cell, cell nucleus, protein molecule, water molecule, atom © Pearson Education Ltd 2015. Copying permitted for purchasing institution only.

Quick Quiz 6 A microscope has a ×5 eyepiece lens and a ×5 objective lens. What is the total magnification? ×25; 5 × 5 = 25 7 A human hair has a width of 100 µm but appears 20 mm wide in a photo. What magnification is the photo? ×200; 20 mm = 20 000 µm; 20 000 ÷ 100 = 200 © Pearson Education Ltd 2015. Copying permitted for purchasing institution only.

Quick Quiz 8 How many millimetres are there in a metre? 1000 9 What unit is 1000 times smaller than a millimetre? micrometre, µm 10 What is the unit symbol for a nanometre? nm © Pearson Education Ltd 2015. Copying permitted for purchasing institution only.

Quick Quiz 11 Why can we see images in more detail with an electron microscope? They have a greater magnification and resolution © Pearson Education Ltd 2015. Copying permitted for purchasing institution only.