Studying Cells - How Microscopes Work
- Created by: Isabelle_Aubrey
- Created on: 13-03-18 18:37
View mindmap
- Studying Cells - How Microscopes Work
- Magnification is Size, Resolution is Detail
- Magnification is how much bigger the image is than the specimen (the sample you're looking at).
- It's calculated using this formula: magnification = image size / object size.
- Resolution is how detailed the image is.
- More specifically, it's how well a microscope distinguishes between two points that are close together.
- If a microscope lens can't separate two objects, then increasing the magnification won't help.
- More specifically, it's how well a microscope distinguishes between two points that are close together.
- Magnification is how much bigger the image is than the specimen (the sample you're looking at).
- You Need to be Able to Calculate the Magnification of an Image
- In the exam, you might be told the actual and magnified size of an object and then be asked to calculate the magnification. You can do this using the formula.
- You might also have to rearrange the formula to work out the image size or object size.
- In the exam, you might be told the actual and magnified size of an object and then be asked to calculate the magnification. You can do this using the formula.
- You Need to Know About Three Types of Microscope
- Light microscopes
- Light microscopes use light.
- They have a lower resolution than electron microscopes - they have a maximum resolution of about 0.2 micrometres.
- So they're usually used to look at whole cells or tissues.
- The maximum useful magnification of a light x 1500 microscope is about
- Laser Scanning Confocal Microscopes (a special type of light microscope)
- Laser Scanning Confocal Microscopes use laser beams (intense beams of light) to scan a specimen which is usually tagged with fluorescent dye.
- The laser causes the dye to fluoresce - give off light.
- The light is then focused through a pinhole onto a detector.
- The detector is hooked up to a computer, which generates an image
- The image can be 3D.
- The detector is hooked up to a computer, which generates an image
- The light is then focused through a pinhole onto a detector.
- The pinhole means that any out-of-focus light is blocked, so these microscopes produce a much clearer image than a normal light microscope.
- They can be used to look at objects at different depths in thick specimens
- Electron Microscopes
- Electron microscopes use electrons instead of light to form an image. They have a higher resolution than light microscopes so give more detailed images. There are two kinds of electron microscope:
- Transmission electron microscope (TEM) - use electromagnet-s to focus a beam of electrons, which is then transmitted through the specimen
- Denser parts of the specimen absorb more electrons, which makes them look darker on the image you end up with.
- TEMs are good because they provide higher resolution images (so they can be used to look at a range of organelles) but they can only be used on thin specimens.
- Denser parts of the specimen absorb more electrons, which makes them look darker on the image you end up with.
- Scanning electron microscopes (SEM) - scan a beam of electrons across the specimen.
- This knocks off electrons from the specimen, which are gathered in a cathode ray tube to form an image.
- The images produced show the surface of the specimen and can be 3D.
- But they give lower resolution images than TEMs.
- The images produced show the surface of the specimen and can be 3D.
- This knocks off electrons from the specimen, which are gathered in a cathode ray tube to form an image.
- Transmission electron microscope (TEM) - use electromagnet-s to focus a beam of electrons, which is then transmitted through the specimen
- Electron microscopes use electrons instead of light to form an image. They have a higher resolution than light microscopes so give more detailed images. There are two kinds of electron microscope:
- Light microscopes
- You Need to be able to compare Magnification and Resolution
- You need to know about the magnification and resolution of light microscopes and both types of electron microscopes.
- Magnification is Size, Resolution is Detail
Similar Biology resources:
Teacher recommended
Comments
No comments have yet been made