bio10-exercise-1-microscopy.pdf
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General Biology
First Sem. A.Y. 2015-2016
Instrument used to make fine details visible
Device used to observe/study small and/or
detailed objects that are too small to be seen by
the naked eye
The microscope must accomplish three tasks:
– Create a magnified image of the specimen (magnify)
– Separate details in the image (resolve)
– Render the details visible to the eye, camera, or other imaging device (contrast)
Uses light
Uses electron beams
LIGHT MICROSCOPE
ELECTRON MICROSCOPE
o Refers to the use of transmitted light to observe specimens
SIMPLE COMPOUND
Simple glass magnifiers
Convex lenses
Uses a single lens to enlarge the object in one step
Two-stage magnification
The objective projects a magnified image into the draw tube of the microscope and the eyepiece further magnifies the image projected by the objective.
Virtual Image -
“Floating” in space about about 10 in below the top of the observation tube where the eyepiece is inserted.
Accurate representation of the specimen (detail, shape, color/intensity)
1. Optical Parts
2. Mechanical Parts
Mirror or Electric Lamps
Source of illumination
Provides light which is needed to view the specimen
Mirror has concave and plane side
Objectives / Objective Lenses
Gathers the light passing through the specimen and then projects an accurate, real, inverted IMAGE of the specimen up into the body of the microscope.
Scanner
Low power objective (LPO)
High power objective (HPO)
Oil immersion objective (OIO)
Eyepiece / Ocular lens
“Looks at” the focused, magnified image projected by the objective and magnify that image a second time (usually 10x) as a virtual image seen as if 10 inches from the eye.
Can be fitted with scales or markers or pointers or crosshairs that will be in simultaneous focus with the focused image.
Condenser
Substage component that gathers light from the light source and concentrates it into a cone of light that illuminates the specimen with uniform intensity over the entire field of view.
Iris diaphragm
Substage component that controls the amount of light that would enter the condenser
Closing the iris diaphragm will increase contrast at the cost of resolution
Numerical aperture
Resolving power and resolution
Magnifying power
Working distance
Numerical Aperture: width of the cone of light that can enter the objective lens.
A property of the lens, usually written on it.
The measure of the light gathering power of the lens
𝐍𝐀 = n (sin µ)
n = refractive index of the mediumµ = half of the angular aperture
MEDIUM n
Air 1.00
Water 1.33
Glycerine 1.47
Oil 1.515
The ability of the microscope to distinguish between two close objects as separate and distinct
Resolution: The smallest distance between two points
on a specimen that can still be distinguished as two separate entities.
Factors that affect resolving power and resolution
Numerical aperture of the objective
Wavelength of illuminator
Where:
R = Resolution or resolving distance
𝝀 = wavelength of illuminator
NA = numerical aperture
R = 𝝀
𝟐 𝑵𝑨
OBJECTIVE TYPE
Plan Achromat Plan Fluorite Plan Apochromat
Magnification
N.AResolution
(µm)N.A
Resolution(µm)
N.AResolution
(µm)
4x 0.10 2.75 0.13 2.12 0.20 1.375
10x 0.25 1.10 0.30 0.92 0.45 0.61
20x 0.40 0.69 0.50 0.55 0.75 0.37
40x 0.65 0.42 0.75 0.37 0.95 0.29
60x 0.75 0.37 0.85 0.32 0.95 0.29
100x 1.25 0.22 1.30 0.21 1.40 0.20
N.A. = Numerical ApertureWavelength
(nanometers)Resolution
(micrometers)
360 .19
400 .21
450 .24
500 .26
550 .29
600 .32
650 .34
700 .37
The ability of a lens to magnify an object
The degree to which an object is enlarged/reduced in size
2 types
Linear Magnification
Magnification of illustration
𝒍𝒊𝒏𝒆𝒂𝒓𝒎𝒂𝒈𝒏𝒊𝒇𝒊𝒄𝒂𝒕𝒊𝒐𝒏 = 𝒎𝒂𝒈𝒏𝒊𝒇𝒊𝒄𝒂𝒕𝒊𝒐𝒏𝒐𝒃𝒋𝒆𝒄𝒕𝒊𝒗𝒆 ×𝒎𝒂𝒈𝒏𝒊𝒇𝒊𝒄𝒂𝒕𝒊𝒐𝒏𝒐𝒄𝒖𝒍𝒂𝒓
Objective Mobj Mocu * LM
Scanner 4x 10x 40x
LPO 10x 10x 100x
HPO 40x 10x 400x
OIO 100x 10x 1,000x
*varies per ocular used. Some oculars have 15-20x magnification.
𝒎𝒂𝒈𝒏𝒊𝒇𝒊𝒄𝒂𝒕𝒊𝒐𝒏 𝒐𝒇 𝒊𝒍𝒍𝒖𝒔𝒕𝒓𝒂𝒕𝒊𝒐𝒏 =𝒔𝒊𝒛𝒆𝒅𝒓𝒂𝒘𝒊𝒏𝒈
𝒔𝒊𝒛𝒆𝒂𝒄𝒕𝒖𝒂𝒍
8 µmDrawing scale!
Given: size of illustration = 9cm; actual size of specimen = 5 um
𝒎𝒂𝒈𝒏𝒊𝒇𝒊𝒄𝒂𝒕𝒊𝒐𝒏 𝒐𝒇 𝒊𝒍𝒍𝒖𝒔𝒕𝒓𝒂𝒕𝒊𝒐𝒏 =𝟗 𝒄𝒎
𝟓 𝝁𝒎
8 µm
𝒎𝒂𝒈𝒏𝒊𝒇𝒊𝒄𝒂𝒕𝒊𝒐𝒏 𝒐𝒇 𝒊𝒍𝒍𝒖𝒔𝒕𝒓𝒂𝒕𝒊𝒐𝒏 =𝟗 𝒄𝒎
𝟎. 𝟎𝟎𝟎𝟓 𝒄𝒎
𝒎𝒂𝒈𝒏𝒊𝒇𝒊𝒄𝒂𝒕𝒊𝒐𝒏 𝒐𝒇 𝒊𝒍𝒍𝒖𝒔𝒕𝒓𝒂𝒕𝒊𝒐𝒏 = 𝟏𝟖, 𝟎𝟎𝟎𝐱
Distance between the tip of the objective and the specimen.
↑ magnification - ↓ working distance
↑ NA ↑ magnifying power
↑ NA ↑ resolving power
↑ magnifying power ↓ working distance
Base, Pillar and Arm Provide stability and
mechanical support to the microscope
Houses electrical components for operating and controlling the intensity of the lamp (base)
Supports the structures that hold the objective and ocular lenses (arm)
Supports the stage and substage (pillar)
Inclination joints*
Stage
Supports the specimen to be viewed
Has an opening for passing the light (stage aperture)
Specimens are held in place using the stage clips
Specimens can be moved using the stage knobs
Nosepiece
Holds the objectives of various magnifications
Dust shield
Prevents dirt from settling on the objectives
Body tube
Holds the nosepiece and dust shield
Draw tube
Holds the oculars in place
Adjustment knobs*
These elevate or lower the stage in larger (coarse) or smaller (fine) increments
Coarse adjustment knob is used to bring the specimen into view
Fine adjustment knob used bring specimen into focus
Condenser adjustment knobs
These elevate or lower the condenser to adjust contrast
Iris diaphragm lever
Controls the diameter of the iris diaphragm
OLD NEW
OLD NEW
Objectives 3 4, Spring-loaded
Range of magnification 100-970x 40-1,500x
Adjustment knobs Separate Combined
Coarse adjustment knob Moves the body tube Moves the stage
Illumination Natural or artificial light reflected through a
mirror
Electric lamp
Condenser knob Absent Present
Stage Immovable, can be tilted Movable, parallel
Stage clips Fixed Movable
Inclination joint Present Absent
Number of ocular 1 1-2
Produces 2D image of greater detail
Produces 3D image for examination and dissection of whole specimens
BRIGHTFIELD STEREOSCOPE
BRIGHTFIELD STEREOSCOPE
Magnification 40-1,000x Maximum of 50x
Orientation of image Inverted Upright
Movement of object across field
Opposite Same
Type of image produced
2D, Virtual 3D, Real
• Uses electron beams to magnify objects smaller than about 0.2µm, such as viruses and specific cell organelles
• Can magnify objects up to 100 000 times
• Better resolution is due to shorter wavelengths of electrons
• Images produced are always black and white
LIGHT MICROSCOPE ELECTRON MICROSCOPE
Source of “illumination”
Visible light Electron beams
Lens system Glass Electromagnets
Medium Air/Oil Vacuum
Specimen holder Glass slide Copper mesh grid
Maximum resolution 0.2µm 0.0025nm
Maximummagnification
2,000x 100,000x
Specimen Live or dead Dead
Image produced 2D 2D or 3D
Color of image Colored Black and white
Objects seen Frog’s eggs, cells, nuclei, mitochondria, lysosomes,
chloroplasts, flagella, cilia, cell wall, cell membrane
Ribosomes, endoplasmic reticulum, Golgi body, proteins, lipids, viruses, small molecules
LIGHT MICROSCOPE ELECTRON MICROSCOPE
1. Turn on the lamp and set the intensity for comfortable viewing.
2. Place the prepared slide on the stage and center it over the stage opening.
3. Raise the condenser into its position.
4. Turn the coarse adjustment knob to lower the stage until it stops.
5. While looking down the ocular, slowly focus upward with the coarse adjustment knob until the specimen comes into view.
6. Manipulate the diaphragm lever to reduce or increase the light intensity to produce the clearest, sharpest image.
7. For a higher magnification, center the specimen in the field of view, then rotate the HPO into position while watching from the side.
8. Focus using the fine adjustment knob.
It should take very little movement of the adjustment knob to bring the image into focus (parfocality).
A particle in the image centered in the field of view should remain in the center as objectives are changed (parcentricity).
1. Focus the specimen with the 10x objective. Then switch to the 40x objective and center a desired feature in the field of view.
2. Turn the nosepiece slightly (objectives are not set) and gently place a drop of immersion oil on top of the cover slip.
3. Rotate the immersion oil objective into the light path.
4. Use the fine adjustment knob until the specimen comes into focus.
Ocular Micrometer
Stage Micrometer
10 20 30 400
Calibration constant = Stage Units x 0.01 mm*
Ocular Units
= 4 x 0.01 mm
6
Calibration constant = 0.00667 mm
* 1o micrometers can be used instead of 0.01 mm
Actual size = Ocular units x C.C.
= 17 x 0.00667 mm
= 0.113 mm
10 20 30 400
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