Chapter 1: week 1 Flashcards
with practice 4 + 5
3 Concepts Of Microscopy
- Magnification
- Contrast
- Resolving Power/ Resolution
3 Concepts of Microscopy: Magnification
the amount that the image of an object is enlarged
the number of times the image is enlarged
3 Concepts of Microscopy: Contrast
the degree to which image details stand out against its background
(striking difference between similar objects)
-we use stains to increase contrast
3 Concepts of Microscopy: Resolving power/ Resolution
the ability of a lens to separate between small objects that are close together
(quality of lens)
Field of View
when looking into the oculars, the portion of the slide that can be observed
Parfocal
when you change from one objective to another, the specimen will remain very nearly in focus
Parcentral
when changing objectives the specimen will stay in the center of the field of view
(when focused properly)
Use of Light in Microscopy
to be able to see objects (specimen) through a microscope, light must be either reflected from the object or transmitted through the object
Properties of Light
- Reflection
- Transmission
- Absorption
- Refraction
Properties of Light: Reflection
Light may be reflected back from the object
(bounce off as it hits object)
-the particular wavelengths reflected back to the eye determine the perceived color
Properties of Light: Transmission
refers to the passage of light through an object
Properties of Light: Absorption
if light rays neither pass through nor bounce off, but are taken up by the object
-the absorbed light rays are reemitted as longer wavelengths, a phenomenon known as fluorescence
Properties of Light: Refraction
the bending of light as it passes from one medium to another of a different density
Types of Microscopes
- Light Microscope
2. Electron Microscope
Types of Microscopes: Light Microscope
-maximum magnification = 2000x
-living or non-living specimens
-color image
(use visible light)
Types of Microscopes: Electron Microscope
- Maximum Magnification = 1,000,000x or more
- non-living specimens only
- black and white image
Types of Light Microscopes
- Stereo-dissecting Light
2. Compound Light
Types of Light Microscopes: Stereo-dissecting Light
- 3D view of specimen = used to view large specimens
ex: frogs, worms, insects - illuminated from above and below
- Magnification up to 45x
Types of Light Microscope: Compound Light
-2D views of the specimen = used to view thin sections of specimens
Types of Electron Microscopes
- Scanning (SEM)
2. Transmission (TEM)
Types of Electron Microscopes: Scanning (SEM)
-3D views of specimens = used to view external surfaces of specimens
(think about scanning the outside (external))
Types of Electron Microscopes: Transmission (TEM)
-2D views of specimens = used to view internal structures of species
(think about transmission= through so you see internally (inside))
Microscope Parts
- Oculars/Eyepieces
- Body/Body Tube
- Arm
- Nosepiece
- Objectives
- Stage/ Mechanical Stage
- Stage adjustment knobs
- Rheostat
- Substage Condenser
- Diaphragm control dial
- Light source/ illuminator
- Base
- Fine adjustment knob
- Coarse adjustment knob
Microscope Parts: Oculars/ Eyepieces
magnify the image 10 fold.
(re-magnifies the image formed by the objective lenses)
-oculars move to accommodate your interpupillary distance- distance between the pupils of your eyes
Microscope Parts: Body/ Body Tube
contains mirrors that bend the light into the ocular
transmits the image from the objective lens to the ocular lens
Microscope Parts: Nosepiece/ Revolving nosepiece
the objectives are attached
-grab black ring of nosepiece to rotate the objectives
Microscope Parts: Objectives
contain lenses that magnify the image
-it has 4x(scanning), 10x(low power), 40x(high dry power), and 100x(oil immersion)
Microscope Parts: Arm
supports the nosepiece, holds the on/ off toggle and focus adjustment knobs
Microscope Parts: Stage/ Mechanical stage
black, flat platform on which your slide rests
Microscope Parts: Stage adjustment knob
moves the mechanical stage
-left, right, toward or away from you
Microscope Parts: Rheostat
increases or decreases light output from the light source
Microscope Parts: Substage Condenser
made of atleast 2 lenses that focus the light passing through the specimen and improve image sharpness
Microscope Parts: Diaphragm control dial
controls the amount of light entering the substage condenser from the light source (adjusts the light)
(has each objectives magnificaton as light power
ex. 4x, 10x, 40x and 100x)
Microscope Parts: Light source/ Illuminator
illuminator is a halogen bulb that produces light
light source
Microscope Parts: Base
holds the light source and supports rest of microscope
Microscope Parts: Fine adjustment knob
possible to bring the image into sharp focus when rotating the knob.
- Raises + Lowers the stage in small increments
- use with high dry 40x and oil immersion 100x
Microscope Parts: Coarse adjustment knob
moves the stage up and down by larger increments and allows you to bring the image into focus
-use with scanning 4x and low power 10x only
Total Magnification
the magnification, or power of a lens is indicated by a whole number followed by an “X”
-the total magnification of a microscope is obtained by multiplying the power of the ocular times the power of the objective
Formula for Total Magnification
TM = Ocular Power X Objective Power
Total Magnification for each objective
Name Ocular Mag. Objective Mag. Total Mag.
Scanning 10x x 4x = 40x
low 10x x 10x = 100x
High 10x x 40x = 400x
Oil 10x x 100x = 1000x
Working Distance
approximate distance from the objective to the specimen (slide)
-working distance decreases as you increase magnification by changing objectives
Depth of Field
refers to the thickness of the plane of focus
- with a large depth of field, all the threads can be in focused at the same time
- with a smaller or narrower depth of field, only one thread or part of one thread can be focused, everything else will be out of focus
