MicroscopesCompound Light Microscope

Electron Microscopes(TEM and SEM)

Overview of Microscopes

• Magnification – increase of an object’s apparent size• Total magnification: mag. of eyepiece x

mag. of objective lens• Ex: (10X) x (4X) = 40X

• Resolution (resolving power) – the distance needed to distinguish 2 points as separate

• Three types of microscopes: compound light, transmission electron, scanning electron

Resolving PowerThe human eye is capable of distinguishing objects

down to a fraction of a mm. With the use of light and electron microscopes it is possible to see down to an

angstrom and study everything from different cells and bacteria to single molecules or even atoms.

 

Compound Light Microscope

• Specimen is enlarged as light passes through set of glass lenses

• Can be used to view living specimens

• Resolving power is limited to the physical character of light – up to 200 nm

• Magnification up to 2000x • beyond ~2000x the image becomes

blurry

Transmission Electron Microscope

• Cannot be used to view living specimens

• Transmits a beam of electrons focused by a set of magnetic lenses through a specimen

• Creates a flat image

• Magnification – up to 200,000x

• Resolution – up to 0.2nm

TEM image

Transmission electron microscope image of a human leukocyte (also known as a white blood cell), showing the Golgi apparatus, which is a structure involved in

protein transport in the cytoplasm of the cell.http://www.sciencelearn.org.nz/Contexts/Exploring-with-

Microscopes

Scanning Electron Microscope:

• Cannot be used to view living specimens

• A narrow beam of electrons is pass over the surface of the specimen, which is coated with a thin layer of metal, producing a 3D image

• Magnification up to 100,000X

• Resolution – up to 10 nm

SEM image

A head louse clasping a human hair. The image was taken using an SEM at 110x magnification. At low magnifications like this,

SEM generates three-dimensional images that are in focus throughout the depth of the sample.http://www.sciencelearn.org.nz/Con

texts/Exploring-with-Microscopes

Microscope Images

http://remf.dartmouth.edu/imagesindex.html

Microscope Comparison

http://www.sciencelearn.org.nz/Contexts/Exploring-with-Microscopes/Sci-Media/Interactives/Which-microscope

Parts of a Microscope

Parts & Function

A. Eyepiece or Ocular Lens – contains a magnifying lens usually 10x magnification

B. Arm – connects to base and supports the body tube; when carrying microscope one hand must hold the arm

C. Coarse focus – raises and lowers the stage or body tube for focusing image; use on LOW power objective only

D. Fine focus – slightly moves the stage or body tube to sharpen (adjust) the image; use on Medium or High power objective

Parts & Function

E. Base – supports the microscopeF. Light source/Illuminator/Projection

Lens – produces light or reflects light up toward the eyepiece (may be a mirror)

G. Diaphragm – regulates the amount of light passing up toward the eyepiece.

H. Stage – supports the slide being observed

I. Stage Clips – holds slide firmly in place

Parts & Function

J. High Power Objective Lens – focuses minute details on slide; provides a magnification of 40x

K. Medium Power Objective Lens – after finding image on low power, use to sharpen image; provides a magnification of 10x

L. Revolving Nosepiece – holds the objectives and can be rotated to change magnification

M. Body Tube – maintains the proper distance between the eyepiece and the objectives

N. Low Power Objective Lens – 1st objective used for focusing; provides a magnification of 4x (10x if no Medium power objective lens)

Care & Handling Microscopes

1. Always carry the microscope in an upright position with two hands.  One hand should support the base and the other should be on the on the arm. Do NOT swing the microscopeCORRECT!!

! INCORRECT!!!

Care & Handling Microscopes

2. Never touch lens with your fingers! Oil produced from your body smudges the glass.

3. Use lens paper and lens cleaning solution to clean the lenses on the microscope. 

Paper towel will scratch the lenses. Use a soft cloth to clean other parts of the

microscope.

Care & Handling Microscopes

3. Always set your microscope on a clean, flat surface.

4. When finished with the microscope, always remove slides from the stage.

Rotate the nosepiece to the lowest  power. Clean stage with lens paper.

Use of the Microscope

Carry microscope with one hand under base and grasp arm with other hand

Gently place the microscope on the table with arm facing you.

Raise body tube by turning the course adjustment knob until the objective lens is about 2 cm above the opening of the stage.

Rotate the nosepiece so that the low power objective is directly in line with the body tube.

Use of the Microscope

Look through the eyepiece and switch on the lamp or adjust mirror to that a circle of light can be seen. Moving the diaphragm lever permits a greater or

smaller amount of light to come through the opening of the stage.

Place prepared slide on the stage so that the specimen is over the center of the opening. Use stage clips to hold slide in place.

Use of the Microscope

Look at the microscope from the side. Carefully turn the coarse adjustment knob to raise the stage until the low power objective almost touches the slide or until the body tube can no longer be moved. Do NOT allow the objective to touch the slide

Look through the eyepiece and observe the specimen. If the field of view is out of focus, use the course adjustment knob to LOWER the stage while looking through the eyepiece until the object comes into focus. You are moving the slide AWAY from the objective lens

Use of the Microscope

Focus the image as best you can with coarse adjustment knob. Then use fine adjustment knob to focus the image more sharply.

Adjust diaphragm lever to allow the right amount of light to enter.

To change the magnification, rotate the nosepiece until the desired objective is in line with the body tube. ONLY use FINE adjustment knob with medium and high power lens FIRST use medium power lens to sharpen image. SECOND use high power lens to focus minute details.

Cyclops

Cyclops under microscope Cyclops are crustaceans and related to lobsters, crabs and

shrimp.   They are invertebrates with a hard outer shell.  They swim freely about.

The cyclops has 5 pair of legs and a divided tail-like appendage called a furca.  The Cyclops is very small about 2-3mm long with one black or red eye in the middle of its head. The cyclops is named after the one-eyed monster of Greek legend.  It is greenish, straw yellow, or grayish in color.  It goes jerking through the water usually in very large numbers. The females carry the eggs (shown in picture) in little side sacs and they multiply rapidly. The cyclops is often seen near water fleas or Daphnia.  Many water animals feed upon the cyclops.  It has a very important role in the food chain.