Microscopy Flashcards
What is the Compound light microscope (bright-field microscope) used for?
Examine cellular structures that are too small to be seen with the naked eye
What are the two magnifying lenses?
- Objective Lens
- Ocular lens (eye piece)
What is the Critical factor resolution achieved by the microscope?
Ability to see structures as separate and distinct
What are the 5 basic terminology of microscopy?
- Resolution
- Magnification
- Numerical Aperture (NA)
- Resolving Power
5.Definition
What is Resolution:
- Indicates how small individual objects can
be and still be recognized as distinct. - Separation of two distinct points/objects
- The more detail seen, the higher the resolution
What is the equation for calculating Magnification:
Magnification Equation: Total Magnification = Objective x Ocular
What is Numerical Aperture (NA):
light gathering ability of the system
It’s the ability of the microscope to render the finest detail distinctly visible
Empty Magnification:
Further magnification of two dots that are no longer resolvable (cannot be distinguished) is considered empty magnification
What is Resolving Power:
The ability of a lens to separate two distinct points
This is the limit of usable magnification
What is Definition:
- The ability of the objective lens to make the outline of an object distinct.
- An object, if poorly defined, is unlikely to be well-resolved even if the lens system has a high resolving power
- Definition is a function of the object and its illumination
What are the functional categories of the microscope?
- Foundational structures
- Slide Holder
- Light Controls
- Magnification System
- Focus Adjusters
What components make up the foundation Structure?
- Base
- Arm
What components make up the Slide Holder?
- Mechanical Stage
- Slide Holder
- Stage Adjustment Knobs (Co-axial knobs)
What components make up the Light Controls?
- Light Source
- Rheostat
- Field Diaphragm
- Condenser
- Condenser Adjustment Knob
- Condenser Centering Screws
- Iris Diaphragm
What components make up the Magnification System?
- Objective Lenses
- Rotating/Revolving Nosepiece
- Ocular Lens
- Diopter Rings
What components make up the Focus Adjusters?
- Coarse Adjustment Knob
- Fine Adjustment Knob
What parts of the microscope are found in the base?
1.Transformer
2.Rheostat
3.Illuminator (lamp)
What is the Transformer:
- Usually located in the base
- Some have an external transformer
- Steps down the voltage or amount of energy entering the illuminator or lamp
What is the Rheostat:
- The dimmer switch located on the base or on the external transformer
- Light intensity regulator
- Controls amount of current entering the illuminator
What is the purpose of the Illuminator (lamp):
1.Provides the major illumination to light the specimen
- Usually located at the back of the base
- If there is a separate on/off switch from the rheostat, then the rheostat must be turned down prior to turning off the microscope in order to increase the life of the bulb
- Light source is then directed up through the condenser
- The bulb must be correctly positioned for proper alignment
6.Tungsten or Tungsten-halogen bulbs are most frequently used
What parts of the microscope are found in the Condenser?
- Centring Screws
- Filter Holder
- Aperture Iris Diaphragm
Centring Screws
- Found on either side of the condenser
- Used to center the condenser over the light
- Condenser and centering screws are used in conjunction with the field diaphragm and light source to control light path from the lamp to the objective lens
- These adjustments are referred to as Koehler illumination
Filter Holder
A swing out attachment at the bottom of the condenser
Easily swings into the light path
It is used to hold light-absorbing filters (blue, green, daylight filters)
Purpose of the coloured or selective filters is to control the contrast in the image of a coloured microscopic preparation (i.e. blood film)
Should be used in precise microscopy where fine detail is important
Aperture Iris Diaphragm
Can be used to adjust the diameter of the light beam passing through the objective lens so that it will just fill the front lens of the objective
This can help to reduce spherical aberration
Spherical aberration is when many focal points produce a blurry image
Field diaphragm
Controls the circle of light in the field of view when specimen and condenser are properly focused
Light sources passes through the field iris diaphragm
The size of the field diaphragm is controlled by rotating a knurled ring, which is concentric with it
Condenser Adjusting Knob
Located in the middle of the body of the microscope (usually on the left-hand side)
Knob raises and lowers the condenser so that the lens focuses the light source directly on the specimen
The top of the condenser lens should lie just under the slide
Focusing Knobs
Located on both sides of the microscope
Knobs used to adjust the position of the stage to bring the specimen being examined into focus and to obtain a clear image
The coarse adjustment knob is the largest knob
Permits the movement over large distances and should only be used when the low power objective (10x) is in place
Then you can get a sharper focus with the fine adjustment knob
Mechanical stage
The platform just above the condenser
Supports the object to be examined (your specimen slide)
Has a central hole through which the light from the substage condenser passes through the specimen
Metal spring clips hold your slide
What is the Vernier Scale:
There are rulers on the right-hand side and the “top” of the stage
Used to quickly re-locate a particular cell or object at a later time
Slide holder function and location:
Holds your slides secure and steady during observation this is located on the stage.
Co-axial adjustment knobs:
Moves in two directions front to back and left to right.