Microscopy and Magnification

• What is microscopy?

  Using microscopes to see tiny things
• What do light microscopes use to make images larger?

  Light and lenses
• Why are microscopes important in biology?

  They help study cells and tissues
• What can light microscopes let us see?

  Individual cells and large cell parts
• What are the key components of light microscopes?

  Light source and lenses
• How do light microscopes compare to electron microscopes?

  They have lower magnification and resolution
• What do scanning electron microscopes (SEM) use to create images?

  An electron beam
• How does SEM create a 3D image?

  By collecting secondary electrons emitted from the surface
• What is the main difference between light microscopes and SEM?

  SEM reflects electrons, while light microscopes pass light
• What is magnification?

  How much bigger an object appears
• What is resolution?

  How clear the image is
• How can magnification be compared to a digital photo?

  Magnification is like zooming in on a photo
• How do electron microscopes compare to light microscopes?

  They have higher magnification and resolution
• What is the formula for magnification?

  $magnification =$$\frac{image\ size}{real\ size}$
• If a cell is 2 μm wide and appears 200 μm wide, what is the magnification?

  $100$
• What is standard form?

  A way of writing very big or small numbers
• What are the key components of standard form?

  A number between 1 and 10, and a power of 10
• How do you convert a number to standard form?

  Move the decimal point and determine the power of 10
• What happens when you move the decimal point to the left in conversion?

  You use a positive exponent for the power of 10
• Convert 0.0025 to standard form.

  $2.5 \times 10^{-3}$
• What are the key uses of light microscopes?

  • Viewing individual cells
  • Observing cell structures like nuclei
• What are the key components of electron microscopes?

  • Electron beam
  • Detector for secondary electrons
• Compare magnification and resolution in microscopy.

  • Magnification: How much bigger an image appears
  • Resolution: How clear an image is
• What is the process for converting numbers to standard form?

  1. Move the decimal point
  2. Determine the power of 10
• What is the relationship between magnification and resolution in electron microscopes compared to light microscopes?

  • Electron microscopes have higher magnification
  • Electron microscopes have higher resolution
• What is the name of the microscopy technique shown in the image?

  Scanning Electron Microscopy (SEM)

  
• What is the purpose of the electron source in an SEM?

  To generate the electron beam that scans the sample

  
• What is the role of the condenser lenses in an SEM?

  To focus the electron beam onto the sample

  
• How does the function of the scanning coil differ from the objective lens in an SEM?

  The scanning coil scans the electron beam across the sample, while the objective lens focuses the beam onto the sample

  
• What are the main components of an SEM?

  • Electron source
  • Condenser lenses
  • Aperture
  • Scanning coil
  • Objective lens
  • Back-scattered electron detector

  
• How does an SEM produce 3D images?

  • The electron beam scans across the sample surface
  • Back-scattered electrons are detected
  • The intensity of the detected electrons is used to construct a 3D topographical image

  
• What type of samples are suitable for SEM imaging?

  • Solid, non-living samples
  • Samples that can withstand high vacuum conditions
  • Samples that can tolerate the electron beam

  
• How does the resolution of an SEM compare to a light microscope?

  • SEM has a much higher resolution (down to 1 nm) compared to light microscopes (limited by the wavelength of light to ~0.2 μm)
  • This allows SEM to image much finer details on the sample surface