MICROSCOPE

All biologists used things such as balances, dissecting tools and computers. One of the most important tools is the MICROSCOPE.

A microscope is an instrument used to study objects too small to be seen and observed by the unaided eye. It greatly increases the amount of data available for scientific inquiries.

The hand lens has been around for over 600 years and is considered as a simple microscope. The first microscope was invented in 1595 by Zacharias and Hans Janssen.

Janssen’s microscope composed of three draw tubes with lenses inserted into the flanking tubes.

Janssen’s microscope was capable of magnifying images approximately 3x when fully closed and up to 10x when fully extended to the end.

— Anton Van Leeuwenhoek further developed the microscope to different shape and magnification.

— His microscope could magnify up to 300x.

— He was the first to view protozoans and bacteria.

Robert Hooke's microscope is the microscope used in discovering the cell.

Kinds of Microscope:

1. Light microscope – uses light to form an enlarged image of the specimen or object being viewed.

a.) simple microscope – single lens or curved piece of glass

b.) compound light microscope – contains two kinds of lenses, the ocular and objective lenses

v Magnification – apparent increase in the size of an object

v Resolving power – ability of a microscope to increase the visible detail of a specimen.

c.) stereomicroscope – used to study large specimens; has an ocular lens and

objective lens for each eye

- arrangement of lenses provides a three-dimensional view of

the specimens surface magnified 50 to 60 times

d.) phase-contrast microscope – clarifies features inside living cells

- special lenses of this microscope use this

interference to reveal boundaries between cell parts,

which appear brighter to the viewer

2. Electron Microscope

- creates enlarged images with a beam of electrons instead of a beam of light

- introduced by the scientists in 1935

- produced both high magnification and high resolution

2 kinds of electron microscopes:

a.) transmission electron microscope – sends beam of electrons through the specimen; the beam creates a clear detailed image on a television like screen magnified 200,000 times or more

b.) scanning electron microscope – sends beam of electrons across the specimen from left to right, a process called scanning

Parts of a Compound Microscope:

1. arm – supports the body tube
2. ocular or eyepiece – contains the magnifying lens you look through
3. body tube – maintains the proper distance between the eyepiece and the objective lenses
4. revolving nosepiece – holds the high and low power objective lenses and can be rotated to change magnification.
5. objective lenses

low power objective (LPO) – provides 10x magnification

high power objective (HPO) – provides 40x magnification

6. stage clips – hold the slide in place
7. stage – supports the slide being viewed
8. diaphragm – regulates the amount of light
9. mirror – reflects the light
10. base – supports the microscope
11. coarse adjustment knob – moves the body tube up and down
12. fine adjustment knob – moves the body tube slightly to sharpen the image

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SELF-TEST

1. What is a microscope?

2. What is a compound microscope?

3. What are the lenses on a microscope called?

4. How should a microscope be carried?

5. How is the total magnification of a microscope determined?

6. What is the purpose of the mirror and diaphragm?

7. What is the purpose of the adjustment knob?

8. What do the clips hold?

9. What is magnification? resolution?