Salman Bin Abdulaziz Salman Bin Abdulaziz University University

College of PharmacyCollege of Pharmacy

Pharmacognosy Department Pharmacognosy Department

Pharmacognosy - I - Lab. (PhG - 222)

The The MicroscopeMicroscope

Lab. 3

The The microscopemicroscope is an is an instrument designed to make fine instrument designed to make fine details visible. The science of details visible. The science of investigating small objects using investigating small objects using such an instrument is called such an instrument is called microscopymicroscopy. .

It is used in a wide range of It is used in a wide range of scientific fields, where major scientific fields, where major discoveries in biology, medicine discoveries in biology, medicine and materials research are based and materials research are based on advances in microscopy.on advances in microscopy.

The microscope must The microscope must accomplish three tasks:accomplish three tasks:

produces a magnified image of the specimen (magnification),

separates the details in the image (resolution),

renders the details visible to the eye, camera, or other imaging device (contrast).

Electron Microscopy

(Electron beams)

MICROSCOPY

Optical Microscopy(electromagnetic waves)

Optical microscopy:

The optical microscope, often referred to as the "light microscope", uses visible light and a system of lenses to magnify images of small samples.

Our eyes are capable of distinguishing color and sensing differences in brightness or intensity ranging from black to white and all the gray shades in between.

Simple microscope:

A simple microscope is a microscope that uses only one lens for magnification, and is the original light microscope.

Light microscopes are able to view specimens in color, an important advantage when compared with electron microscopes, especially for forensic analysis, where blood traces may be important, for example.

Compound Light Microscope:

The term light refers to the method by which light transmits the image to your eye. Compound deals

with the microscope having more than one lens.

Simple light microscopes of the past could magnify an object to 266X. Modern compound light microscopes, under optimal conditions, can magnify an object from 1000X to 2000X (times) the specimen's original diameter.

Applications of Compound Micrscope :

Optical microscopy is used extensively in microelectronics, nanophysics, biotechnology, pharmaceutical research and microbiology. It is used for medical diagnosis, the field being termed histopathology when dealing with tissues.

Microscopy is also becoming an important tool for forensic scientists who are constantly examining hairs, fibers, clothing, blood stains, and other items associated with crimes.

Applications of Compound Micrscope :

Optical microscopy is best suited to view stained or naturally pigmented specimens such as stained prepared slides of tissue sections.

It is useless for living specimens of bacteria, or any unstained cell suspensions or tissue sections.

Stereo microscope:

The stereo or dissecting microscope uses two separate optical paths with two objectives and two eyepieces to provide slightly different

viewing angles to the left and right eyes.

In this way it produces a three-dimensional visualization of the sample

being examined.

The stereo microscope is often used to study the surfaces of solid specimens or to carry out

close work such as sorting, dissection, microsurgery, and watch-making.

It usually has a binocular eyepiece and a range of magnifications typically from 5x to 35 or

40x.

Digital microscope:

A digital microscope is a variation of a traditional optical microscope that uses optics and a charge-coupled device (CCD) camera to

output a digital image to a monitor.

A primary difference between an optical microscope and a digital microscope is the

magnification. With an optical microscope the magnification is found by multiplying the lens magnification by the eyepiece magnification.

Electron microscope

An electron microscope is a type of microscope that produces an

electronically-magnified image of a specimen for detailed observation. It has a

greater resolving power than a light-powered optical microscope.

It can achieve magnifications of up to 100,00 x, whereas light microscopes are

limited to 2000 x magnification.

Electron microscopes are used to observe a wide range of biological and inorganic

specimens including microorganisms, cells, large molecules, biopsy samples, metals,

and crystals.

Image of glandular hairs under electron microscope

Care of the microscope

EVERYTHING on a good quality microscope is unbelievably expensive, so be careful.

Hold a microscope firmly by the stand, only. Never grab it by the eyepiece holder, for example.

Always make sure the stage and lenses are clean.

NEVER use a paper towel, your shirt, or any material other than good quality lens tissue or a cotton swab (must be 100% natural cotton) to clean an optical surface.

Be gentle! You may use an appropriate lens cleaner or distilled water to help remove dried material. Organic solvents may separate or damage the lens elements or coatings.

Cover the instrument with a dust jacket when not in use.

Focus smoothly; don't try to speed through the

focusing process or force anything. For example if you encounter increased resistance when focusing then you've probably reached a limit and you are going in the wrong direction.

Care of the microscope

Preparation of the Specimen:

Add the plant material in a clean slide.

Add few drops of reagent, like chloral hydrate.

Heat using Bunsen flame for few minutes (never let the slid dry).

Put the cover slip on the slide in an angle 45° and lower slowly to drive out any air bubbles.

Before examination be sure that the cover is clean and the area not covered by the cover slip is clean and dry.

Notes on using microscopes:A. Place your microscope on a secure

table, free from vibration, to begin.

B. Turn on the lamp and set the intensity for comfortable viewing.

C. Place a specimen slide on the stage.

D. You must learn to view through the eyepiece(s) with both eyes open!

E. Start from the beginning by low power (4 X).

Notes on using microscopes:

F. If you wish to move to a higher power objective, it should take very little movement of the fine adjustment knob to bring the image into focus.

G. If the specimen does not come into view (does not focus), raise the tube a little with the coarse focus knob and attempt to focus again with the fine focus knob. Once the object is in focus, switching objective lenses (to a higher power) should be possible without any further coarse adjustments.