Which microscope produces images with a dark background?
Which microscope produces images with a light background?
List the types of microscopy in order of increasing resolution.
Compound Microscope (up to 2000), Scanning Electron Microscope (SEM) 1000-10,000x, Transmission Electron Microscope (TEM) 10,000-100,000x, Scanning Tunneling Microscope
Which types of microscopy give surface images?
Differential Interference Contract (DIC), Scanning Electron Microscope (SEM)
Which types of microscopy give internal images?
Brightfield, Darkfield, Transmission Electron Microscopy (TEM), Phase Contrast Microscopy, Confocal
What are the three main ways to view an object with a microscope?
Which stain would you use if you wanted to separate gram positive from gram negative specimens?
Which units are most useful for measuring bacteria?
Nanometer (NM), Micrometer (UM)
To improve the resolution of a light microscope, how would the light have to be altered?
Use immersion oil
How is refraction prevented with immersion oil?
Immersion oil has the same refractive index as the slide, prevents the light from refracting between the specimen and the objective lens, resulting in a sharper image.
What are the advantages and disadvantages of brightfield?
Inexpensive, easy to use, cannot view very small specimens
What are the advantages and disadvantages of darkfield?
Can examine living organisms that do not stain well
What are the advantages and disadvantages of phase contrast?
No staining required, produces a detailed color image of internal structures in living organisms.
What are the advantages and disadvantages off luorescent?
Allows rapid detection and identity of microbes in tissues or specimens.
What are the advantages and disadvantages of Differential Interference Contrast (DIC)?
No staining required, specimen appears colored, 3D images with fine detail.
What are the advantages and disadvantages of electron microscopy (transmission, scanning, STM)?
Can see smaller specimens than light microscope, higher magnification and resolution. Harder to use and very expensive.
What are the advantages and disadvantages of confocal?
Color can be added and 3D images can be generated
What happens to resolving power as the numerical aperture increases? decreases?
Increases: You can see the space between objects that are farther apart. Decreases: You can see the space between objects that are closer together
What is the resolution of a lens with 43x magnification, NA of 1.45 and using red light with a wavelength of 900 nm? How about a 97x lens with the same NA and light?
What is the usual reason to stain a specimen?
To change the refractive index of a specimen so that it is contrasted enough to view
How does a simple basic stain differ from a simple acidic stain?
Basic dyes are positive so they are attacted to negative bacteria and stain. Acidic dyes are negative so they don't stain bacteria which are also negative, they stain background instead.
What are the 4 main steps of a Grams stain? What is the purpose of each?
1. Cover with purple dye which stains all cells (primary stain) 2. Wash off purple dye and cover with iodine, a mordant. Wash off iodine. 3. Wash slide with alcohol (decolorizing agent) 4. Stain with safranin, a basic red dye.
What is the difference between a differential stain and a simple stain?
Differential stains only stain certain bacteria. Simple stain highlights the entire microorganism
What are 3 different special stains?
Negative Staining for Capsules, Endospore Staining and Flagella Staining