Learning Objectives Chapter 2 Flashcards
Magnification
Ability to enlarge an image
Resolution
Ability to distinguish two adjacent objects as distinct and separate
Refraction
Light bending through a medium
Bright-Field Microscopy
Create images by bending light. Light is refracted when passing from one medium to another.
Oil Immersion Lens
100x objective lens with short working distance. Oil is required to give a clear image
Why must specimens often be stained in bright-field microscopy
In order to increase contrast
Phase-Contrast Microscopy
Produces an image of a darker specimen against a lighter background. Good for observing movement and detecting bacterial structures.
Why do specimens not need to be stained in phase-contrast microscopy
The phase ring amplifies differences in the refractive index of a call and surroundings
How are magnification and resolution controlled in a microscope
Dark-Field Microscopy
Image is formed by light reflected or refracted by the specimen. Produces a bright image of the object against a dark background. Living and unstained specimens
Fluorescence Microscopy
Produces an image by exciting the specimen with a wavelength of light that triggers the object to emit fluorescent light. Can rely on natural fluorescence or specimen can be stained. Used in clinical diagnostic microbiology.
Confocal Scanning Laser
uses a laser beam to illuminate a fluorescently labeled specimen. Creates a sharp 3d image by using aperture that eliminated stray light. Used to study biofilms.
Transmission Electron Microscopy
Heated tungsten filament in electron gun directs a focused beam of electrons on specimen. denser = darker image. Specimen is cut thinly
Scanning Electron Microscopy
Electrons scatter off the specimen surface generating 3D image. Output is digitalized.
Electron Microscopy (TEM and SEM)
Electrons illuminate and allow for visualization of viruses/details of microbial structures.
