Aim #8: The microscope, an instrument in scientific investigation Do Now: If you haven’t handed in the graphing lab, do so now. Homework: Microscope WS. Rephrase questions in your own words. Do NOT answer the question. Due Tomorrow Test corrections due Thursday

Microscope- Fun Facts Many people experimented with making microscopes The first microscope was 6 feet long!!! The Greeks & Romans used “lenses” to magnify objects over 1000 years ago.

1. The History Hans and Zacharias Janssen of Holland in the 1590’s created the “first” compound microscope Anthony van Leeuwenhoek and Robert Hooke made improvements by working on the lenses Anthony van Leeuwenhoek Robert Hooke

The History Zacharias Jansen The “First” Microscope

2. How a Microscope Works Convex Lenses are curved glass used to make microscopes (and glasses etc.) Convex Lenses bend light and focus it in one spot.

2.How a Microscope Works Ocular Lens (Magnifies Image) Objective Lens (Gathers Light, Magnifies And Focuses Image Inside Body Tube) Body Tube (Image Focuses) Bending Light: The objective (bottom) convex lens magnifies and focuses (bends) the image inside the body tube and the ocular convex (top) lens of a microscope magnifies it (again).

3. The Parts of a Microscope

Body Tube Nose Piece Objective Lenses Stage Clips Diaphragm Light Source Ocular Lens Arm Stage Coarse AdjCoarse Adjustment Fine Adjustment Base Skip to Magnification Section

Body Tube The body tube holds the objective lenses and the ocular lens at the proper distance Diagram

Nose Piece The Nose Piece holds the objective lenses and can be turned to increase the magnification Diagram

Objective Lenses The Objective Lenses increase magnification (usually from 10x to 40x) Diagram

Stage Clips These 2 clips hold the slide/specimen in place on the stage. Diagram

Diaphragm The Diaphragm controls the amount of light on the slide/specimen Turn to let more light in or to make dimmer. Diagram

Light Source Projects light upwards through the diaphragm, the specimen and the lenses Some have lights, others have mirrors where you must move the mirror to reflect light Diagram

Ocular Lens/Eyepiece Magnifies the specimen image Diagram

Arm Used to support the microscope when carried. Holds the body tube, nose piece and objective lenses Diagram

Stage Supports the slide/specimen Diagram

Coarse Adjustment Knob Moves the stage up and down (quickly) for focusing your image Diagram

Fine Adjustment Knob This knob moves the stage SLIGHTLY to sharpen the image Diagram

Base Supports the microscope Diagram

5. Magnification To determine your magnification…you just multiply the ocular lens by the objective lens Ocular (10x) & Objective (40x): 10 x 40 = 400x Objective Lens have their magnification written on them. Ocular lenses usually magnify by 10x So the object is 400 times “larger”

10x x 4x = 40x magnification magnification total of eyepiece lens of obj. lens magnification The specimen being viewed is magnified 40 times. The greater the total magnification, the smaller the field of view (FOV) or area that you see. The lower the total magnification, the larger the field of view (FOV).

low

7. Caring for a Microscope Clean only with a soft cloth/tissue Make sure it’s on a flat surface Don’t bang it Carry it with 2 HANDS…one on the arm and the other on the base

7. Using a Microscope Start on the lowest magnification Don’t use the coarse adjustment knob on high magnification…you’ll break the slide!!! Place slide on stage and lock clips Adjust light source Use fine adjustment to focus

What happens to the image AND the field of view as you increase in magnification?

HIGH POWER FIELD OF VIEW -How much can you see? In High Power we see 25% of the low power FOV (low power 100 x is 25% of high power 400x) We see less of the specimen but we see more details of the specimen under high power LOW POWER

FIELD OF VIEW How do we find the FOV of a microscope? Low Power (100x) 1.Find the diameter of the LP FOV 2.Use the clear metric ruler (mm side) 3.Be sure to line up the first mm mark with the left side of the field. LP FOV = 1.5 mm

The mm is too large to measure microscopic objects, so you need to use the micron (micrometer) µm 1 mm = 1,000 µm 1 µm = 1/1000 mm or 0.001mm LP FOV = 1500µm

So how do we determine how big something is in the microscope? Let’s see how it works: Use the following formula: FOV # of cells (that can fit across diameter) FOV = 2mm =.5mm # of 4 cells OR.5mm x 1000 =500 microns

10. Magnification vs. Resolution

The ability of a microscope to distinguish between two points that are very close to one another (to make objects more clear)

Types of Microscopes a. compound microscope uses 2 lenses. b. stereoscope also called a dissection microscope. This has 2 oculars (eye pieces) is used to observe external parts of a specimen.

Electron Microscope The limit of resolution restricts the usefulness of light microscopes for studying VERY small specimens such as viruses. Electron microscopes use a stream of electrons to view these specimens. Electron microscopes have a limit of resolution more than 1000 times finer than light microscopes.