Chapter 3 Observing Microorganisms Through a Microscope

What does the term resolution (resolving power) refer to in microscopy?

• The ability to magnify an image

• Minimum distance between two objects where you can still see them as separate entities

• The ability to change the color of an image

• The ability to focus light on a specimen

How does wavelength affect the resolving power of a microscope?

• Longer wavelengths increase resolution

• Shorter wavelengths decrease resolution

• Shorter wavelengths increase resolution (higher energy)

• Wavelength has no effect on resolution

Which of the following are types of light microscopes?

• Electron, Scanning Probe, Atomic Force, Bright-field, Fluorescence

• X-ray, Infrared, Bright-field, Confocal, Dark-field

• Bright-field, Phase-contrast, Differential Interference Contrast, Dark-field, Fluorescence, Confocal

• Bright-field, Transmission Electron, Scanning Electron, Fluorescence, Confocal

What is the most common type of light microscope, which uses two lenses and is known as a compound microscope?

• Dark-field microscope

• Phase-contrast microscope

• Bright-field microscope

• Fluorescence microscope

What is the maximum magnification and resolution capability of a bright-field microscope?

• 1000X magnification; 0.5 µm resolution

• 2000X magnification; 0.2 µm resolution

• 1500X magnification; 0.3 µm resolution

• 2500X magnification; 0.1 µm resolution

What is the primary function of a phase-contrast microscope?

• It uses fluorescence to highlight structures in a specimen

• It enhances the difference in refractive index of the sample and its surrounding

• It uses electron beams to create high-resolution images

• It provides a three-dimensional view of the specimen

How does a specimen appear when viewed under a phase-contrast microscope?

• Brighter than the surrounding

• The same brightness as the surrounding

• Darker than the surrounding

• Fluorescent against a dark background

What is the key characteristic of a Differential Interference Contrast microscope?

• It uses fluorescence to highlight specific structures in a specimen

• Passes two beams (split light) through a specimen and then recombine out of phase 

• It uses electron beams to produce high-resolution images

• It provides a dark background to enhance specimen visibility

How does a specimen appear when viewed under a Differential Interference Contrast microscope?

• Fluorescent against a dark background

• Darker than its surroundings

• Colored with a 3D appearance

• Transparent with no visible contrast

How does a Dark-Field Microscope create contrast?

• It amplifies differences in refractive index

• It passes light through a specimen at an angle so only refracted light enters the objective

• It separates light into two beams and recombines them out of phase

• Â It uses a fluorescent tag to highlight the specimen