Microscopy

• What is the formula for magnification?


  Magnification= Image/Object
• Make sure to convert units!
• General rule for being seen?

  If the object is smaller than half the wavelength of light, it cannot be seen.
• TEM


  Max magnification is 1,500,000

  Passes a beam of electrons through the specimen, electrons that pass through are detected on a fluorescent screen on which the image is displayed.
• Limitations of TEM

  Thin sections of specimen needed.

  Must be put into a vacuum so the electron beam isn’t disturbed by gas particles. Produces 2D image.
• SEM


  Passes a beam of electrons over the surface of the specimen (scanning beam).

  Electrons reflect off the surface of the specimen which has been coated in heavy metals.

  3D
• Limitations of SEM


  Lower magnification them tem - 1 million.

  In a vacuum.

  Coated in heavy metals.

  Black and white images.
• What is the price range for purchasing a light microscope?


  £100-500
• Why is a light microscope considered cheap to operate?


  Because it does not require expensive materials or maintenance
• What is a key physical characteristic of light microscopes?


  They are small and portable
• What is an advantage of light microscope sample preparation?


  It is simple and easy
• Does a light microscope require a vacuum for operation?


  No, a vacuum is not required
• How does a light microscope maintain the natural color of a sample?


  It does not alter the sample during observation
• What is the maximum magnification of a light microscope?


  2000 times
• Can specimens observed under a light microscope be living?


  Yes, specimens can be living or dead
• What is often needed to make cells visible under a light microscope?


  Stains
• What is the cost of purchasing an electron microscope?


  Over £500,000
• Why is the production of an electron beam considered expensive?


  It requires specialized equipment and maintenance
• What is a key physical characteristic of electron microscopes?


  They are large and require special rooms
• What is a disadvantage of electron microscope sample preparation?


  It is lengthy and complex
• How does sample preparation affect the material in electron microscopy?


  It distorts the material
• Does an electron microscope require a vacuum for operation?


  Yes, a vacuum is required
• What type of images do electron microscopes produce?


  All images are in black and white
• What is the maximum magnification of an electron microscope?


  Over 1,000,000 times
• Why must specimens for electron microscopy be dead?


  They must be fixed in plastic and viewed in a vacuum
• What is a potential issue with the electron beam in electron microscopy?


  It can damage specimens
• What type of chemical is usually used to stain specimens for electron microscopy?


  Electron-dense chemicals, usually heavy metals
• Which heavy metals are commonly used for staining in electron microscopy?


  Osmium, lead, or gold
• How do electron microscopes work?


  Electron microscopes detect electrons on a fluorescent screen.
• Why must specimens be kept in a near vacuum for electron microscopy?


  Specimens must be kept in a near vacuum to prevent the electron beam from being disturbed by gas particles.