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Histology > Ex 1 Microscopy > Flashcards

Ex 1 Microscopy Flashcards

1
Q

Degree of bending depends on

A

Refractive index and angle at which light strikes surface

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2
Q

How does light striking a perpendicular surface travel?

A

It does not bend

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3
Q

Refractive power

A

Measure of how much a lens bends light waves. Measure in diopters.

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4
Q

Focal point

A

The point through which all parallel rays of light will pass after passing through each part of the lens

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5
Q

Focal length

A

The distance from the center of the lens to the focal point

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6
Q

Convex lens make light rays….

A

converge at a focal point

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7
Q

Characteristics of real image

A
  • object outside of focal point
  • inverted
  • can be projected on screen
  • different size from object
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8
Q

Virtual image characteristics

A
  • not inverted
  • cannot be projected
  • can be magnified
  • object inside focal point
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9
Q

Compound microscope make….

A

virtual image from real image and the object will be inverted

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10
Q

Resolution

A

The ability of a microscope (or any other instrument) to distinguish small points as separate points

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11
Q

Resolution formula

A

0.6lambda/nsinalpha

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12
Q

How does distance affect resolution

A

The smaller the distance the better the resolution because the distance between the two points is smaller and we want to be able to see objects that are very close together.
We want to increase denominator and decrease the numerator.

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13
Q

How do you improve resolution/

A

Use higher refractive index or shorter wavelengths

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14
Q

Compound optical microscope

A

Light microscope, bright-field microscope

  • light source
  • condenser
  • stage
  • objective lens
  • ocular lens
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15
Q

Pros and cons of compound optical microscope

A
  • ability to magnify
  • ability to resolve structural detail
  • specimen must be thin
  • relatively little contrast in unstained specimen
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16
Q

Phase contrast microscope

A

Converts phase shifts (invisible to the eye) in light passing through a transparent specimen to brightness changes (visible to eye) in the image
-can be used to examine unstained cells and tissues
-useful for examination of living cells
-

17
Q

Refractive index

A

velocity of light inside transmitting medium

18
Q

1 diopters =

A

1 meter divided by the focal length of the lens

19
Q

How do you obtain a real image with greater magnfication?

A

Having the object as close as possible to the focal point of a lens with a very short focal length

20
Q

When you see a virtual image, are you seeing converging or diverging rays?

A

Diverging- no point exists at any plane in space ta which rays radiating from the object are brought to a focus

21
Q

What is the highest resolution in a light microscope? Transmission electron microscope?

A

Light: 0.5um (micrometers)
TEM: theoretically 0.01A realistically 5-10A (0.5-1.0nm)

22
Q

Why can we not see at 0.01A using a TEM?

A

The electrons have refraction and bending and form clouds

So we can see molecules but we cannot see individual atoms.

23
Q

Fluorescence Microscope

A
  • detects molecules that emit light of wavelengths in visible range when exposed to UV light source
  • detects naturally occurring fluorescent molecules such as Vitamin A
24
Q

Most widespread use of fluorescence microscope?

A
  • detection of antigens/antibodies in immunochemical staining procedures
  • detection of fluorescent tracers injected into animals or cells
25
Q

How does the confocal scanning microscope increase optical resolution and contrast?

A

Adds a pinhole placed at the confocal plane of the lens to eliminate out-of-focus light

26
Q

Confocal Scanning Microscope

A
  • Combines light microscope, fluorescence equipment, and a scanning system that employs a laser beam
  • laser light is strongly convergent and produces a shallow scanning spot on specimen
  • light emerging from spot is directed to a photomultiplier tube and analyzed
  • a mirror system moves the laser and records date from each spot
  • computer uses 3D reconstruction and subtracts out the out of focusimages
27
Q

Advantages of confocal scanning microscope

A
  • very thing optical images (1um thick)
  • out of focus images are subtracted out
  • computer can make 3D reconstruction
28
Q

Transmission Electron Microscope

A
  • uses electron beam instead of light
  • cathode and anode drive electrons through column (potential difference imparts an accelerating voltage of 20,000-200,000 volts
  • series of electromagnets (condenser, objective, and projection lenses) control electrons
  • specimen holder, viewing screen, photographic film

Histology (7 decks)

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