Biologists use microscopes to study cells, cell parts, andyourscienceteacher.net/wp-content/uploads/2017/09/The-Microscope.pdfParts Of The Compound Light Microscope. It supports the

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

The microscope is among

the most widely used tools in

biology.

A microscope is an

instrument that produces an

enlarged image of an

object.

There are Two Types of Microscopes:

Light Microscopes:

Light passes through

one or more lenses to

produce an enlarged

image of a specimen.

ElectronMicroscopes:

Forms an image of

a specimen using a

beam of electrons

rather than light.

The History of the Microscope & Early Cell Studies

Zaccharias Janssen - 1590

Zaccharias Janssen was a Dutch

spectacle maker. While

experimenting with several

lenses in a tube, he discovered

that nearby objects appeared

to be greatly enlarged.

This was the first very

simple compound

microscope.

Zaccharias Janssen - 1590

A compound microscope is

one that has two sets of

lenses.

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

Although Hooke’s

microscope had

three lenses, they

were of very

____________ and he

could see very

___________.

poor quality

little detail

Drawings made by Robert Hooke

Leeuwenhoek was a

Dutch merchant who

experimented with the

grinding of lenses.

He was able to polish

lenses of great curvature

that obtained a

magnification of nearly

300 times.

He built a simple

microscope. A simple

microscope is one that has

only one lens.

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

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”.

• Contains a lens to magnify the image of the specimen.

• Some microscopes have two ocular lenses.

Ocular Lens / Eyepiece

Parts Of The Compound Light Microscope

It connects the eyepiece to the

objective lenses.

Body Tube


• It connects the body tube to the base.

• One hand should be around the arm when carrying the

microscope (the other should be

under the base).

Arm


It supports the weight of

the microscope.

Base


It sends light up through the

condenser lens and through the

hole in the stage onto the

specimen on the slide.

Older microscopes used to use

mirrors.

Light Source


The objective lenses are attached to

it. Rotating the nose piece allows you

to switch between the different

lenses.

Revolving/Rotating Nosepiece


These lenses further magnify the

image of the specimen. The

magnifications are usually 4X, 10X

and 40X. There are usually 3 lenses.

4 X

10 X

40 X

Objective Lenses


The first knob you should use, and

always under low power. Never

use it in high power. Moves the

stage up and down.

Coarse Adjustment Knob


Use under higher power for

exact focusing.

Fine Adjustment Knob


The stage is where you place the slide

containing the specimen.

It has a hole that light passes through

and onto the specimen.

Stage


The stage clips

secure the slide on

the stage.

Stage Clips


The lens under the stage

that focuses light from the

light source to the hole in

the stage.

Condenser Lens


It contains a dial that

rotates to adjust the

amount of light that

reaches the specimen.

Diaphragm


This microscope allows light to

pass through the specimen and

uses two lenses to form an image.

The modern compound

microscope is capable of two

things:

a) Magnification

b) Resolution

The Compound Light Microscope

Magnification is a measure of how much the image is

enlarged.

Total magnification = ocular x objective

4x objective = 10 x 4 = 40 times magnification



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.

1. Always carry the microscope by the arm with the

other hand supporting the base.

2. Turn on the microscope and place your slide on

the stage.

3. Always start with the 4x objective. Focus this

objective using the course adjustment knob.

4. Once the image is in focus, carefully swing the 10x

objective in place. Refocus this objective using the

course adjustment knob.

5. Once the image is in focus, very carefully swing the

40x objective into place. Focus this objective using

ONLY the fine adjustment knob.

6. Never use the coarse adjustment knob while using

the high power objective.

7. Keep the stage dry and always make sure the

bottom of your slide is dry before putting it on the

microscope.

8. Return your objective to low power before you put

the microscope away.

Preparation of a Wet Mount Slide

Most of the slides we will make are wet mount slides.

Wet mount slides are used to view living organisms, as

well as liquid substances of all kinds.

They are also used for any sort of specimen that needs

to be kept damp.

Steps to Making a Wet Mount Slide

1. Obtain a clean, dry slide.

2. Put your specimen in the center of the slide.

3. Add one large drop of water. (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.

4. Hold a clean coverslip at a 45 degree angle over the specimen.

Allow one edge of the coverslip to touch the edge of the drop of water.

5. Gently drop the coverslip into place.

6. The whole coverslip should be in contact with water, but make

sure the back of the slide is dry.

As the power increases, the

magnification becomes larger, but

the field of view (visible area)

becomes smaller.

Resolution is the limiting factor to a light microscope.

At greater magnifications, the light microscope is

unable to resolve the image. At powers of

magnification beyond 2000X the image becomes

blurry.

To examine cells or cell parts at magnifications greater

than 2000x, scientists use electron microscopes.

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 vacuum chamber so

that the electrons in the beam will not bounce

off gas molecules in the air. Since living things

cannot survive in a vacuum, the electron

microscope cannot be used to view living

cells.

Electron microscopes are much more powerful

than light microscopes.

Dust mite

Pollen

SEM: Scanning Electron Microscope

TEM: Transmission Electron Microscope

TEM: Transmission Electron Microscope

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

Advantage:Disadvantage:

Magnification up to 200,000

times.

The method used to

prepare the specimen

will kill the cells so that

living cells cannot be

observed.

The specimen is not sliced for viewing, but the specimen

is sprayed with a fine metal coating. Like the

transmission electron microscope living cells cannot be

viewed.

When the beam of electrons is passed over the specimen’s

surface, it causes the metal coating to emit a shower of

electrons. A 3D image of the surface of the specimen is

projected on a photographic plate.

The scanning electron microscope can magnify 100,000 times.

SEM: Scanning Electron Microscope

Documents

Biologists use microscopes to study cells, cell parts, andyourscienceteacher.net/wp-content/uploads/2017/09/The-Microscope.pdfParts Of The Compound Light Microscope. It supports the