CHAPTER 2

• What is microscopy?


  The technology of making very small things visible to the human eye.
• What does wavelength (λ) refer to in microscopy?


  The distance between two adjacent crests or troughs of a wave.
• How does the value of λ affect the resolving power of a lens?


  The smaller the value of λ and the larger the value of NA, the greater the resolving power.
• What is the relationship between the wavelength and the electromagnetic spectrum in microscopy?


  The shorter the wavelength used, the greater the resolution that can be attained.
• What does resolution refer to in microscopy?


  The ability to see two items as separate and discrete units rather than as a fuzzy, overlapped single image.
• What is resolving power in microscopy?


  The ability of film, lens, or both together to reproduce fine detail.
• What occurs during reflection in microscopy?


  Light strikes an object and bounces back, giving the object color.
• What does it mean if an object is phosphorescent?


  The object continues to emit light when light rays no longer strike it.
• What does transmission refer to in microscopy?


  The passage of light through an object.
• What occurs during absorption in microscopy?


  Light rays neither pass through nor bounce off an object but are taken up by the object.
• What is refraction in the context of light?


  The bending of light as it passes from one medium to another of different density.
• What does diffraction refer to in microscopy?


  Light waves are broken up into bands of different wavelengths as they pass through a small opening.
• What is the main feature of brightfield microscopy?


  It uses visible light of illumination and cannot resolve structures smaller than about 0.2 µm.
• How does darkfield microscopy differ from brightfield microscopy?


  Darkfield microscopy uses a special condenser that blocks light from entering the objective lens directly.
• What is the purpose of phase-contrast microscopy?


  To facilitate detailed examination of the internal structures of living specimens.
• What is the role of the annular diaphragm in phase-contrast microscopy?


  It allows direct light to pass through the condenser, focusing light on the specimen.
• What is the main feature of differential interference contrast microscopy?


  It uses two beams of light separated by prisms, producing colored images.
• What is the purpose of fluorescence microscopy?


  To detect and identify microbes in tissues or clinical specimens using fluorescent-antibody techniques.
• What is the main advantage of transmission electron microscopy?


  It can resolve structures smaller than 0.2 µm due to the shorter wavelength of electrons.
• What is the purpose of scanning acoustic microscopy?


  To examine living cells attached to another surface, such as cancer cells and biofilms.
• What does scanning tunneling microscopy reveal?


  It reveals the bumps and depressions of the atoms on the surface of the specimen.
• What is the purpose of atomic force microscopy?


  To provide images of biological molecules in nearly atomic detail and molecular processes.
• What is the difference between brightfield and electron microscopes?

  Electron microscopes use a beam of electrons rather than light, allowing for higher-resolution images.
• Which microscopy techniques produce three-dimensional images?

  • Differential Interference Contrast
  • Confocal Microscopy
  • Scanning Electron Microscopy
  • Atomic Force Microscopy
  • Scanning Tunneling Microscopy
• What is a stain (dye) in microscopy?


  A molecule that can bind to a cellular structure and give it color.
• What is the purpose of using stains in microscopy?


  To make organisms stand out against their background and examine structural differences.
• What are the two main types of stains?

  Simple stain and differential stain.
• What does a simple stain do?


  Uses a single dye to reveal cell shapes and arrangements.
• What does a differential stain do?


  Uses two or more dyes to distinguish between different organisms or parts of an organism.
• Why are artificial dyes important in microscopy?


  They are products of chemical derivatives from substances in coal tar.
• What are acid-fast microorganisms?


  A group of bacteria that resist decolorization by acids during staining procedures.
• Why do acid-fast microorganisms resist decolorization?


  Due to the presence of mycolic acid in their cell walls.
• Why are acid-fast microorganisms significant?


  They include some of the most common and dangerous human pathogens.
• What are the components of a dye compound?

  The chromophore and auxochrome.
• What is a chromophore?


  An atom or group of atoms responsible for the color of a compound.
• What is an auxochrome?


  A group of atoms attached to a chromophore that increases the color of a molecule.
• How does the number of auxochromes affect the color of a compound?


  The greater the number of auxochromes, the deeper the color of the compound.
• What is a chromogen?


  A benzene plus chromophore group.
• What gives the dye its affinity for bacteria or tissues?

  The auxochrome.
• What determines whether a dye is cationic or anionic?

  The auxochrome.