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 Leeuwenhoek1632-1723

Robert Hooke 1635-1703

The History

Zacharias Jansen1588-1631

The “First” Microscope

2. How a Microscope Works

Convex Lenses arecurved glass used to make microscopes(and glasses etc.)

Convex Lenses bendlight and focus it inone spot.

2.How a Microscope WorksOcular 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

ObjectiveLenses

Stage Clips

Diaphragm

Light Source

Ocular Lens

Arm

Stage

Coarse 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 tomake 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 magnificationwritten 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

8.- 9. 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 We see less of the specimen but we see more details of the specimen under high powerdetails 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

0.001mmLP 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 4cellsOR .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 asviruses.• 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.