The scanning electron microscope





The SEM is used to produce three-dimensional images of the surface of specimens. Electron are reflected from the surface of a specimen stained with a heavy metal. This enables the SEM to produce images of whole specimens: cells, tissues, or even organisms.

Although electron microscopes have revolutionized cell biology, they have not completely replaced light microscopes. Light microscopes are used to examine living and unstained specimens. Preparation of specimens for electron microscopy is complicated and time-consuming. Electron microscopes are very expensive and can be used only to study dead specimens stained with heavy metal, which might well produce artifacts.

■ Glossary of essential terms for you to know.

English term Russian equivalent
magnified увеличенный
specimen образец, особь
to explore исследовать
toinvent изобретать
lens линза
to refract преломлять
magnification увеличение
apparent видимый
compound составной, сложный
blurred смазанный
to distinguish различать
resolution разрешение
wavelength длина волны
clarity ясность, четкость
beam луч, пучок лучей
ray луч
internal внутренний
sample образец
to impregnate оплодотворять, пропитывать, насыщать
stain пропитка
readily легко
to reflect отражать
to enable позволять
tissues ткани
to replace заменять

■ Your Essential Assignments

I. Quick check

1. How is the magnification varied in:

a) a light microscope

b) an electron microscope?

2. Why is the resolving power of an electron microscope so much better than of a light microscope?

3. What is the approximate size of the smallest structure that can be observed with a light microscope?

 

II. Fill in the missing words:

Term (verb) Noun Adjective
magnify ....... .......
multiply ....... .......
reflect ....... .......
absorb ....... .......
prevent ....... .......

III. Use monolingual English dictionary and write down what could the words given below mean:

microscope, to refract, magnification, sample, ray.

 

IV. Match these words with their definitions:

1. beam A. a piece of curved glass which makes things look bigger or smaller
2. toinvent B. the power of a microscope to give a clear picture of things, or a measure of this
3. eyepiece C. to change the position of the lens on a microscope so that you can see something clearly
4. lens D. to make a substance spread completely through something
5. resolution E. a shining line of light from the sun, a lamp
6. to focus F. a picture of a subject in a mirror or in the lens of a camera
7. specimen G. easily noticed
8. to impregnate H. to make, design, or produce something new for the first time
9. image I. made up of two or more parts or substances
10. apparent J. a small amount or piece of something that is taken from a plant or animal, so that can be tested or examined
11. compound K. the glass piece that you look through in a microscope

V. Find English equivalents to the following word combinations:

Russian term English equivalent
1. научное использование микроскопов  
2. электронный микроскоп  
3. стеклянные линзы  
4. окуляр  
5. видимый размер объекта  
6. зависеть от ч.-л.  
7. длина волны света  
8. без потери четкости  
9. сканирующий электронный микроскоп  
10. внутренняя структура клетки  
11. легко проходить через ч.-л.  
12. трехмерное изображение  
13. поверхность образца  

VI. Give Russian equivalents to the following English terms:

English term Russian equivalent
a magnified image of sth.  
a compound light microscope  
to pass through  
to refract (bend) the light  
structures lying close together  
the resolving power  
to be limited by sth.  
a beam of light  
thetransmission electron microscope  
to focus an image  
to produce clear images  
complicated and time-consuming  
dead specimens  
pass readily through the lightly stained parts  
to be impregnated with sth.  

VII. Find synonyms among the pool of words:

Pool of words Synonyms
1)1. multiply /2. sample /3.increase /4. specimen  
2)1. image / 2. visible / 3. apparent / 4. picture  
3)1.beam/2.refract/3.examine/4.bend/5.explore/6. ray  
4)1.organism/2.compound/3.living thing/4. complex  

VIII. Answer the following questions. Use all information given before:

1. What are microscopes used for?

2. What types of microscopes are most commonly used today?

3. What is a compound light microscope?

4. What does the magnificationof an instrument depend on?

5. How do electron microscopes differ from compound light microscopes?

6. What are the main types of electron microscopes?

7. What is the difference between thetransmission electron microscope and the scanning electron microscope?

 

IX. Match the sentence halves. Make complete centences:





Рекомендуемые страницы:


©2015-2019 poisk-ru.ru
Все права принадлежать их авторам. Данный сайт не претендует на авторства, а предоставляет бесплатное использование.
Дата создания страницы: 2017-04-03 Нарушение авторских прав и Нарушение персональных данных

Обратная связь

ТОП 5 активных страниц!