The Microscope

Heba Al-Tamimi

The Microscope The eye has a resolving power of about 0.01 mm, so

how can eyes distinguished two points which are less than 0.1 mm apart as two separate points ?

We can use a tool called a light microscope to observe and examine microstructures which are smaller than 0.1 mm

Main concept Magnification : is the ratio of an object’s image size to its

real size

Resolution :- is the minimum distance two points can be separated and still be distinguished as two points

Contrast :- refers to increasing differences between the lightest and darkest parts of an image thus making them easier to distinguish

So many specimens are stained with artificial dyes like hematoxylin :stain nucleus eosin : stain cytoplasm

Common Microscope Types

Dissecting Compound Electron microscope

Parts of a compound light microscope The parts of a microscope may be grouped into three

systems : Mechanical system : forms the skeleton of microscope

and includes the tube ,arms ,nosepiece ,base ,stage ,and focusing knobs

Illuminating system : concentrates light on specimen and usually consists of a light source, a condenser lens and an iris diaphragm

Imaging system : magnifies the image of the specimen and improves its resolution and includes ocular and objective lenses

Mechanical system

Arm

Focusing knobs

Base

Stage

Nosepiece

Tube

Body tube: Connects Ocular to

Nosepiece

nose piece: Rotates to allow for the

changing of objectives to increase or decrease magnification.

Stage: Platform on which a

microscope slide rests

Stage clips Used for adjusting the

position of the slide for viewing

Stage

Stage clips

Arm:A secure part of the

microscope to carry the microscope with

Base:provides support for

microscope

Coarse Adjustment Knob Moves the stage or body tube up and down to get the

proper working distance

Fine Adjustment Knob This knob moves the stage SLIGHTLY to get a sharp

image of the specimen (critical focusing)

Illuminating system

Condenser lensCondenses the light rays passing though the specimen

Light source Iris diaphragmregulates the amount of light passing through the slide

Imaging system

Ocular Lens/Eyepiece Magnifies the image of the specimen ( 10x) microscope have one lens monocular Two lenses binocular

Objective lenses Magnify specimens

being examined

Lens magnification: Low (4x) Medium (10x) High (40x) Oil lens (100x)

TOTAL MAGNIFICATION Power of the eyepiece (10X) multiplied by the power of each

ofthe objective lenses determines total magnification.

The Parts of the MicroscopeMagnification

Support body tube

Supports slide

Focuses image

Sharpens the image

Supports microscope

Reflects lighttowards eyepiece

Regulatesamount of light

Holds slide In place

Hold objectives-rotates to changemagnification

Magnification

Maintainsproper distancebetween lenses

Proper Procedures1. Carry the microscope by

holding the arm with one hand and supporting the base with the other hand

2. Place microscope ~5 cm from the edge of the bench .

3. Clean the microscope lenses and slides by using lens paper

4. Plug the microscope into the mains, and turn on the light

Proper Procedures5. Rotate the nosepiece to obtain

the proper objective lens Make sure the lens clicks into

place!!

6. Place slide on stage, center specimen over stage

Proper Procedures7. Start your study by using

low power objective to have a general idea ,to know more details shift to medium power and finally the high power objective

8. Focus image using fine adjustment knob

Avoid damaging slide!Do not use course adjustment knob with high power!

NOTE When you study wet mount make sure that the slide is

covered with a cover slip.

When finishing your work, don’t leave slides on stage of your microscope .

If any part of your microscope is damaged or is not working well, tell your instructor .

Storing the Microscope

the 4 X objective is in the upright (vertical)position

the stage is all the way down

the power is off the cord is wrapped

properly around the base

At the end of your work and before returning your microscope to its proper cabinet make sure of the following

Preparation of a wet mount

Note Add a drop of water and cover with a cover slip by holding the cover slip at

a 45 angle to the drop of water with one edge of the cover slip on the slide.

Then gently and slowly lower the cover slip over the drop to get rid of air

bubbles.

The dissecting(stereoscopic) microscope

Three dimensional image (3-D) Much larger working distance Viewing objects which are too

large to see under light microscope

true image (not inverted) Magnification (7-45 X) Specimen moved same

direction as image Reflected light

Phase contrast microscope This microscope allows

study of living specimens without killing them .

So we can study cell division locomotion of cell and

organelles

Transmission electron microscope (TEM) Source of illumination is electron

beams Magnification may reach 1,000,000

X and resolution 0.2 nm Sections used are as thin as 60-100

nm Sections are stained with heavy

metals So this microscope is used to study

the ultrastructure (details )of a cell.

Scanning electron microscope (SEM) This type of microscope

scans the surface of a specimen which is coated by a thin layer of gold

Source of illuminating is electron beams

Eyepiece

Arm

Stage

Course adjustment

Fine adjustment

Base

Let’s Review!

12.

13.

9.

10.

11.

14.

Body tube

Nosepiece

Low power

High power

Stage clips

Diaphragm

Light source

Medium power

1.

2.

3.

4.

5.

6.

7.

8.

Go To Work……