Lecture 4: Microscopy

90° polarized light

A light wave that is oriented at a 90-degree angle to another, used in polarized microscopy to enhance contrast of birefringent materials.

Acid-fast stain

A differential stain that detects organisms with waxy mycolic acid in their cell walls, such as Mycobacterium species.

Atomic force microscope

A high-resolution type of scanning probe microscope that maps surfaces by measuring forces between a probe and the specimen.

Bright field microscope

A basic light microscope that illuminates the specimen with white light and forms a dark image on a bright background.

Confocal pinhole

A small aperture in a confocal microscope that blocks out-of-focus light, improving optical sectioning and resolution.

Confocal scanning laser microscope

A microscope that uses a laser and pinhole to scan specimens and construct sharp, 3D-like optical sections.

Contrast Dark field condenser

A special condenser that directs light at an angle so only scattered light enters the objective, enhancing visibility of unstained specimens.

Dark field microscope

A microscope that uses angled illumination to make objects appear bright against a dark background, useful for thin or poorly stained specimens.

Differential interference contrast (DIC)

A microscopy technique that converts differences in refractive index into contrast using prisms, producing pseudo-3D images.

Differential stain

A staining procedure that uses two or more dyes to distinguish between different types of microorganisms or cellular components.

Electron cryotomography

A technique combining cryogenic freezing and electron tomography to produce high-resolution 3D reconstructions of cellular structures.

Fluorescence microscope

A microscope that uses a light source to excite fluorophores, which emit light of a different wavelength for imaging.

Fluorophore

A fluorescent chemical compound that absorbs light energy and re-emits it at a longer wavelength, used as a label in microscopy.

Gram stain

A differential stain that classifies bacteria as Gram-positive or Gram-negative based on cell wall structure.

Immersion oil

A transparent oil placed between the specimen slide and objective lens to reduce light refraction and improve resolution at high magnification.

Magnification

The apparent increase in size of an object when viewed through a microscope.

Negative stain

A stain that colors the background instead of the cells, making specimens appear bright against a dark background.

Phase contrast microscope

A microscope that enhances contrast by converting differences in refractive index into variations in light intensity.

Phase plate (phase shifting element)

A microscope component that shifts the phase of light waves passing through different parts of the specimen, enabling phase contrast imaging.

Resolution

The ability of a microscope to distinguish two close points as separate objects.

Scanning electron microscope (SEM)

A type of electron microscope that scans a specimen with a focused beam of electrons to produce detailed surface images.

Simple stain

A staining method that uses a single dye to add contrast between cells and background.

Transmission electron microscope (TEM)

A microscope that passes electrons through a very thin specimen to reveal internal structural details.

Wollaston prism

A specialized optical prism used in DIC microscopy that separates and recombines light rays to create contrast from refractive index differences.