lec 3. Microscopy

This flashcard set covers the fundamental concepts of microscopy, including units of measurement, the properties of light, and the various styles of microscopes such as compound, confocal, and electron microscopy.

Micrometer

A unit of measure ($\mu m$) where $1,000,000\, \mu m = 1\text{ meter}$.

Nanometer

A unit of measure ($nm$) where $1,000,000,000\, nm = 1\text{ meter}$. The wavelength of visible light ranges from $400-700\, nm$.

Angstrom

A unit of measure ($\text{Å}$) where $10,000,000,000\, \text{Å} = 1\text{ meter}$. It is typically used to measure the size of atoms and bond lengths.

Simple microscope

A microscope that utilizes a single convex lens magnifier to create a virtual image.

Compound microscope

A microscope that uses two or more convex lenses aligned in series, typically an objective lens and an eye piece lens, for two-stage magnification.

Numerical aperture (NA)

An estimate of how much light from the sample is collected by the objective; higher $NA$ results in better resolution.

Bright field microscopy

A standard microscopy technique where the sample typically needs to be stained because the image contrast relies on light absorption by the specimen.

Darkfield microscopy

Direct light enters from the side, allowing only scattered light to enter the objective to visualize unstained samples. Not ideal for thick/multilayered specimens, poor contrast for internal structure, requires strong illumination which may damage life specimens.

Phase Contrast Microscopy (PCM)

Transforms phase differences into intensity differences using constructive and destructive interference to increase contrast in unstained samples. Reveals imperfections in surfaces.

Fluorescence Microscopy

Uses fluorochromes where the specimen is exposed to ultraviolet, violet, or blue light (NOT WHITE LIGHT), emitting light of a longer wavelength and less energy. Used to see specific structures inside cells, can detect living/dead cells

Confocal Microscopy

Uses lasers for point-by-point scanning to capture horizontal sectional planes and generate 3D images. Used for getting sample depths. Specimen is stained with fluorochrome. Used to study live and fixed cells

Electroporation

A method to get fluorescent probes into cells by subjecting the cell to a very short electric shock to create transient pores in the membrane.

Scanning electron microscope (SEM)

Scans the surface of a material to create detailed 3D images.

Transmission electron microscope (TEM)

Passes electrons through a thin sample to reveal internal structures.