Unit Two Part II MICROSCOPY

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1 Unit Two Part II MICROSCOPY AVERETT 1 0 /9/2013 1

2 MICROSCOPES Microscopes are devices that produce magnified images of structures that are too small to see with the unaided eye Humans cannot see objects much smaller than 0.1mm in size. Development began in 1500 s and by the 1800 s most microscopes had combinations of lenses that provided clear images. Anton Van Leeuwenhoek, discovered microscopic organisms in pond water (he called them wee beasties ) Robert Hooke was able to recognize the cell as the basic unit of life. AVERETT 1 0 /9/2013 2

3 COMPOUND LIGHT MICROSCOPES Two Types of compound light microscopes Traditional compound light microscope Also just called a compound light microscope Stereoscope Also called dissecting microscope AVERETT 1 0 /9/2013 3

4 COMPOUND LIGHT MICROSCOPES Compound The image is focused by two sets of lenses Ocular lens located in the eyepiece; the lens system closest to the eye. Objective lenses - located near the specimen The image is magnified by both sets of lenses. Light The image is formed through the transmission of light. AVERETT 1 0 /9/2013 4

TRADITIONAL COMPOUND LIGHT MICROSCOPES Use transmitted light to form image Light is transmitted through very thin specimen Translucent will let light through Specimen must be prepared and thin enough

5 TRADITIONAL COMPOUND LIGHT MICROSCOPES Use transmitted light to form image Light is transmitted through very thin specimen Translucent will let light through Specimen must be prepared and thin enough to let light through Can purchase prepared slides Image is formed through a series of lenses Lenses are parfocal - the image remains focused when switching from one objective lens to the next with little refocusing required! AVERETT 1 0 /9/2013 5

6 TRADITIONAL COMPOUND LIGHT MICROSCOPES View through 2 lenses at any one time Ocular lens Found inside eyepiece Magnification power is written on side of eyepiece Objective lenses Can have 2-4 different lenses Magnification power is listed on side of lenses Use rotating nosepiece to change objective lenses!!! The image is magnified by both sets of lenses AVERETT 1 0 /9/2013 6

TRADITIONAL COMPOUND LIGHT MICROSCOPES Staining Thin objects are often colorless Need to add color to be able to see the object Different stains for

7 TRADITIONAL COMPOUND LIGHT MICROSCOPES Staining Thin objects are often colorless Need to add color to be able to see the object Different stains for different objects Handling slides Always hold by edges or sides to avoid fingerprints Cover slip used to cover or protect object being viewed. AVERETT 1 0 /9/2013 7

TRADITIONAL COMPOUND LIGHT MICROSCOPES 2 dimensional image produced Image produced is upside down and reversed from left to right due to orientation of

8 TRADITIONAL COMPOUND LIGHT MICROSCOPES 2 dimensional image produced Image produced is upside down and reversed from left to right due to orientation of mirrors inside microscope Can view living or dead organisms whole small organisms parts of larger specimens natural or man-made objects AVERETT 1 0 /9/2013 8

9 TRADITIONAL COMPOUND LIGHT MICROSCOPE Magnification Degree to which a microscope can enlarge an image compared to the objects real size Today the strongest compound light microscopes are able to magnify objects up to 2,500X Our classroom compound light microscopes have ocular lenses with a magnification power of 10x Our classroom compound light microscopes have objective lenses with a power of 4x, 10x, and 40x AVERETT 1 0 /9/2013 9

TRADITIONAL COMPOUND LIGHT MICROSCOPES Total Magnification The total amount an object is magnified when viewed through a compound light microscope Total magnification is a

10 TRADITIONAL COMPOUND LIGHT MICROSCOPES Total Magnification The total amount an object is magnified when viewed through a compound light microscope Total magnification is a combination of the power of the ocular lens and the power of the objective lens being used Total magnification = ocular lens power X objective lens power AVERETT 1 0 /9/

11 Total Magnification examples: TRADITIONAL COMPOUND LIGHT MICROSCOPES If looking through the ocular lens and using the scanning power objective: 10 x 4 = 40x If looking through the ocular lens and using the low power objective: 10 x 10 = 100x If looking through the ocular lens and using the high power objective: 10 x 40 = 400x What you are seeing is 400 times larger than it is in real life!!! AVERETT 1 0 /9/

12 TRADITIONAL COMPOUND LIGHT MICROSCOPE Resolution, or resolving power, is a measure of the clarity of an image; the measurement of how close two points can be and still be distinguished as separate. AVERETT 1 0 /9/

13 COMPOUND LIGHT MICROSCOPES Objective lenses Scanning, Low power, High power, Oil immersion Parfocal capability ability of the image to remain in focus as move from one objective lens to another with little refocusing! Resolving power the measurement of how close two points can be and still be distinguished as separate. Field of view the area visible through the microscope. As the power of the objective increases, the sixe of the field of view decreases. Focal plane the portion of the specimen on the slide that is in focus at any moment Depth of focus (field) the vertical distance that can be sharply focused on a specimen. As the power of magnification increases, the depth of field/focus decreases. AVERETT 1 0 /9/

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15 STEREOSCOPES Also called dissecting microscopes Use reflected light for form images Light is directed down on the specimen and reflected back into the objectives and eyepieces. Specimen does NOT have to be thin Image orientation is same as object AVERETT 1 0 /9/

16 STEREOSCOPES Paired objectives and ocular lenses Each eye sees image separately Aligned so you only see one 3-D image Objective lenses usually 1x-4x Ours are 2x and 4x Ocular lenses are usually 10x or 15x Ours are 10x AVERETT 1 0 /9/

organisms No preparation needed, object easily manipulated

17 Advantages STEREOSCOPES Able to see small details on large specimens Helpful for dissections of small but visible organisms No preparation needed, object easily manipulated Overall object is easily recognizable AVERETT 1 0 /9/

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ELECTRON MICROSCOPES Developed in the 1950 s Focuses beams of electrons to produce an image on a computer screen Originally black and white (can

19 ELECTRON MICROSCOPES Developed in the 1950 s Focuses beams of electrons to produce an image on a computer screen Originally black and white (can use computer to add color) Can magnify specimens more than 200,000 times their actual size A few can even see individual atoms! AVERETT 1 0 /9/

20 ELECTRON MICROSCOPES Used to view objects 1000x smaller than can be viewed with compound light microscope No living organisms because the specimens being studied have to be in a vacuum. Two main types of electron microscopes Scanning electron microscope (SEM) Transmission electron microscope (TEM) AVERETT 1 0 /9/

21 SCANNING ELECTRON MICROSCOPES Scanning electron microscopes (SEM) Scans the surface with a beam of electrons Surface usually coated with thin layer of metal that deflects the electrons Computer forms 3D image from measurements of the deflected electrons. AVERETT 1 0 /9/

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24 TRANSMISSION ELECTRON MICROSCOPES Transmission electron microscope (TEM) Transmits electrons through a thin slice of a specimen Creates a 2 dimensional image similar to that of a light microscope but with a much higher magnification AVERETT 1 0 /9/

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27 X-rays OTHER IMAGING TECHNOLOGY Formed by x-rays which pass through soft tissues such as skin and muscle, but are absorbed by bones and teeth Good for looking at the skeleton but not muscle, cartilage, ligaments, or organs AVERETT 1 0 /9/

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30 Magnetic Resonance Imaging MRI OTHER IMAGING TECHNOLOGY Strong magnetic field used to produce a cross-section image of a part of the body Functional MRI and show which areas of the brain are active while a person is doing a task. AVERETT 1 0 /9/

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STRUCTURE OF THE MICROSCOPE

STRUCTURE OF THE MICROSCOPE Use the word list to label the microscope below: Light Source Coarse adjustment knob Diaphragm Stage Clips Objectives Fine Adjustment Knob Base Stage Stage Clips Arm Revolving