Microscopy (Practical)

• What is the equation to work out the Image size?

  Actual size x magnification (I=AM)
• What is the primary advantage of microscopes?

  They allow exploration of cell structures beyond the human eye's capability.
• What are the main types of microscopes in use today?

  • Light microscopes
  • Electron microscopes
• What is the function of a light microscope?


  It uses light to illuminate the specimen and allows examination of live organisms.
• What are the limitations of light microscopes?


  They have relatively low resolution and magnification.
• What is the function of an electron microscope?

  It uses a beam of electrons to magnify the image, providing greater detail.
• What is a key limitation of electron microscopes?


  They can only be used to examine dead specimens.
• Why is proper use and handling of a microscope essential?

  To obtain clear and accurate observations.
• Which type of microscope allows us to see large sub cellular structures like nuclei 


  Light microscope
• Advantage and disadvantage of an electron microscope


  Advantage: has a higher resolution and magnification

  Disadvantage: expensive
• What does resolution mean?


  Resolution is the ability to distinguish between two points. For example a higher resolution will give a sharper image
• An electron microscope can see the internal structure of mitochondria and chloroplasts
• What do the actual size and image size have the same of?


  Units
• Why is it better to use standard form while working with cells using microscopes


  The cell can be either really big or small so using standard from can shorten how many zeros we have to add on to the number
• How can you prepare a slide to view onion cells under a microscope? 


  -add a drop of water to the middle of a clean slide

  -cut up an onion and separate them into two layers, uses tweezers to peel of a thin layer of epidermal tissue

  -using the tweezers, place the epidermal tissue of an onion into the water on the slide

  -add a drop of iodine

  -place a cover slip carefully while lowering it on top
• Why mustn’t you get any air bubbles under the cover slip


  It will obstruct the view of the object that is trying to be observed
• Why do we need to add a drop of iodine on the epidermal tissue


  Iodine solution is a stain, stains are used to highlight sub cellular structures in a cell by adding colour to them
• What are the main parts of a light microscope

  -eyepiece

  -high and low power objective lenses

  -coarse adjustment knob

  -fine adjustment knob

  -stage

  -light
• How to use a light microscope to look at the slide

  -clip prepared slide on the stage

  -select the lowest-powered objective lens

  -use the coarse adjustment knob to move the stage up to just below the objective lens

  -look down at the eyepiece, use the coarse adjustment knob to move the stage downwards until the image is roughly in focus

  -adjust the focus with the fine adjustment knob, until a clear image of the object on the slide is visible

  -after you can view it with a greater magnification by swapping to a higher-powered objective lens and refocus
• When describing a method on how to use a light microscope what must you always include


  -how to set up the microscope

  -object that‘s going to be viewed

  -look at it with low magnification and then a higher one

  -draw the image accurately and write the magnification near it and label it, also make a bar scale for the images

  -multiply the objective magnification with eyepiece magnification

  -repeat there steps with other objects
• What is the conversion factor from millimeters to micrometers?

  Multiply by 1000
• How many millimeters are in one meter?

  1000 mm
• How many micrometers are in one millimeter?

  1000 µm
• What is the conversion factor from micrometers to nanometers?

  Multiply by 1000
• How many nanometers are in one micrometer?

  1000 nm
• What is the conversion factor from micrometers to millimeters?

  Divide by 1000
• What is the conversion factor from nanometers to micrometers?

  Divide by 1000
• What is the conversion factor from nanometers to millimeters?

  Divide by 1,000,000
• What should you remember when using a microscope 


  always hold it by the arm when moving it around and understanding the main features of a light microscope
• What are some rules that apply when drawing an image thats viewed on the microscope 


  -draw with a sharp pencil to get clear and unbroken lines

  -all structures drawn should be in proportion

  -label all features using straight, uncrossed lines
• Biological drawings should be as large as possible and should take up about half a page to be sure it is as accurate and clear as it possibly can be
• A coverslip is used to prevent air currents affecting the specimen and also helps to keep the specimen moist
• When looking at cells under a microscope we need to look at them in their natural state which means they must be alive or fixed (preserved) but still able to stain properly
• How to calculate the siza of a single cell

  -clip ruler on top of the slide

  -view ruler and slide under x100 objective lens and adjust focus to obtain clear image

  -line the cells along 1mm and count number of cells that fit that length

  -1mm=1000μm, 1000/number of cells in 1mm, answer unit in μm