The Microscope
The Microscope – An Introduction The microscope is among the most widely used tools in biology. A microscope is an instrument that: produces an enlarged image of an object. Biologists use microscopes to study cells, cell parts, and organisms that are ________ to be seen with the naked eye. Microscopes both _______ the image of an object and ________________. too small enlarge show its details
There are two types of microscopes: Light Microscopes: Electron Microscopes: Light passes through one or more lenses to produce an enlarged image of a specimen. Forms an image of a specimen using a beam of electrons rather than light.
The History of the Microscope and Early Cell Studies Zaccharias Janssen and his son Hans - 1590 Two Dutch spectacle makers, Zaccharias Janssen and his son Hans, while experimenting with several ______________, discovered that: nearby objects appeared greatly enlarged. lenses in a tube
A compound microscope is one that has: two sets of lenses. Zaccharias Janssen and his son Hans - 1590 This was the first very simple compound microscope. A compound microscope is one that has: two sets of lenses.
The Compound (Light) Microscope Some early microscopes… Compound Microscope: This microscope allows light to pass through the specimen and uses two lenses to form an image.
Robert Hooke – 1665 Robert Hooke used a crude microscope to observe a: thin slice of cork. The chambers he saw reminded him of the ___________ in which monks lived, so he called them “_____”. small rooms cells He was the first to use the word “cell” to describe the _________________. smallest units of life.
Drawings made by Robert Hooke. Although Hooke’s microscope had three lenses, they were of very __________ and he could see very _________. poor quality little detail
Anton van Leeuwenhoek – 1674 Leeuwenhoek was a Dutch merchant who experimented with the: grinding of lenses. He built a ______ microscope. A simple microscope is: a microscope that has only one lens. simple He was able to polish lenses of great curvature that obtained a magnification of nearly _________. 300 times
Anton van Leeuwenhoek – 1674 He is considered “______________________” because of the great discoveries he made with his microscopes. He built over ___ different microscopes. The Father of Microscopy 240 Drawings made by Leeuwenhoek
Anton van Leeuwenhoek – 1674 He was the first to… …see and describe microorganisms under a microscope. He observed a drop of pond water teeming with life. He referred to these small microorganisms as “______________”. tiny animalcules He also described bacteria, yeasts, and the circulation of blood through capillaries in the tail of a fish.
The Microscope 1. Ocular: The first lens in a compound microscope. 2. Objective Lens: The second set of lenses in a compound microscope. 3. Body tube: Keeps the two sets of lenses the correct distance apart. 4. Rotating Nosepiece: Allows the user to change objectives. 5. Stage: A place to put the slide. 6. Stage Clips: Holds the slide in place.
The Microscope 7. Diaphragm: Regulates the amount of light that hits the slide. 8. Light source 9. Coarse Adjustment Knob: Moves the stage up and down rapidly. 10. Fine Adjustment Knob: Moves the stage up and down very slowly. 11. Arm 12. Base
The Compound (Light) Microscope This microscope allows light to _______________________ and uses __________ to form an image. pass through the specimen two lenses The modern compound microscope is capable of two things: a) Magnification b) Resolution
Magnification Magnification is a measure of how much the image is enlarged. Total magnification = (ocular) (objective) 4x objective = (10) (4) = 40 times magnification 10x objective = (10) (10) = 100 times magnification 40x objective = (10) (40) = 400 times magnification NOTE: Many oculars have a magnification of 10x, but it is possible for a microscope to have an ocular that magnifies differently.
Resolution Microscopes vary in powers of magnification and resolution. a) A measure of the clarity of an image. b) It is the power to show details clearly. Microscopes vary in powers of magnification and resolution.
Rules for Using the Compound Microscope Always carry the microscope by: the arm with the other hand supporting the base. Turn on the microscope and place your slide on the stage. Please follow these rules when using the microscope: 3. Always start with the __________. Focus this objective using the ____________________. 4x objective coarse adjustment knob Once the image is in focus, carefully swing the ___________ in place. Focus this objective using the ___________________. 10x objective coarse adjustment knob
Rules for Using the Compound Microscope Once the image is in focus, very carefully swing the ___________ into place. Focus this objective using ONLY the __________________. 40x objective Please follow these rules when using the microscope: fine adjustment knob 6. Never use the coarse adjustment knob while using the high power objective. Keep the stage ____ and always make sure the bottom of your ____ is dry before putting it on the microscope. dry slide Return your objective to _________ before you put the microscope away. low power
Preparation of a Wet Mount Slide Most of the slides we will make are ________ slides. Wet mount slides are used to view ______________, as well as _____ substances of all kinds. They are also used for any sort of specimen that needs to be kept _____. wet mount living organisms liquid moist
Preparation of a Wet Mount Slide 1. Obtain a _____________. clean, dry slide 2. Put your _________ in the center of the slide. specimen Add one large drop of ______. (It should be one solid drop of water over the specimen.) It should not… ….run all over the slide or get on the back of the slide. water Hold a clean _______ at a ________ angle over the specimen. Allow one edge of the coverslip to touch the edge of the drop of water. coverslip 5. Gently drop the coverslip into place. 45-degree The whole coverslip should be in contact with water, but make sure the back of the slide is dry.
How to Measure Under the Microscope The unit of measurement used to measure things under the microscope is the _______________. One micrometer = ______________________________. micrometer ( m) .000001 meter or 1/25,000 inch Using the 10x objective… The 10x objective has a field of view with a diameter of 1500m . Estimate the size of the cell in the drawing to the left. With the 10x objective, the size of the cell would be about 400 μm.
How to Measure Under the Microscope Using the 40x objective…. The 40x objective has a field of view with a diameter of 375m. Estimate the size of the cell in the drawing to the left. With the 40x objective, the size of the cell would be about 100 μm.
The Electron Microscope Resolution __________ is the limiting factor to a light microscope. At greater magnifications, the light microscope is unable to ________________. At powers of magnification beyond _____, the image becomes ______. resolve the image 2000x blurry To examine cells or cell parts at magnifications greater than 2000x, scientists use electron microscopes.
Characteristics of the Electron Microscope 1. Does not use light. A beam of electrons produces an enlarged image of the specimen. Both the electron beam and the specimen must be placed inside a _______________ so that the electrons in the beam will not bounce off _____________ in the air. Since ____________ cannot survive in a vacuum, the __________________ cannot be used to view living cells. vacuum chamber gas molecules living things electron microscope Electron microscopes are much more powerful than light microscopes. pollen Dust mite mitochondrion
Electron Microscopes There are two types of electron microscopes: Transmission Electron Microscope Scanning Electron Microscope Transmission Electron Microscope Scanning Electron Microscope
Transmission Electron Microscope (TEM) It uses a ________________ transmitted through a very thinly sliced _________. _______ guide the stream of electrons toward the specimen, and the image is projected on a ________________. stream of electrons specimen Magnets photographic plate Disadvantage: The method used to prepare the specimen will kill the cells so that living cells cannot be observed. Advantage: Magnification up to 200,000 times.
Scanning Electron Microscope (SEM) Provides excellent three-dimensional images. The specimen is not _____ for viewing, but the specimen is _______ with a fine metal coating. Like the transmission electron microscope….. ……living cells cannot be viewed. sliced sprayed When the beam of electrons is passed over the specimen’s surface, it causes the metal coating to emit a shower of electrons. A ____________________ of the _______ of the specimen is projected on a photographic plate. three-dimensional image surface The scanning electron microscope can magnify 100,000 times.