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AQA A Bio Unit 1 Biological Molecules > 3.2: The electron microscope > Flashcards

3.2: The electron microscope Flashcards

1
Q

Light microscopes have poor resolution as a result of the what?

A

Light microscopes have poor resolution as a result of the relatively long wavelength of light

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2
Q

Light microscopes have poor resolution as a result of the relatively long wavelength of light.
In the 1930s however, a microscope was developed that used a beam of electrons instead of light.
An electron microscope has 2 main advantages:
1. The electron beam has a what?

A

The electron beam has a very short wavelength

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3
Q

Light microscopes have poor resolution as a result of the relatively long wavelength of light.
In the 1930s however, a microscope was developed that used a beam of electrons instead of light.
An electron microscope has 2 main advantages:
1. The electron beam has a very short wavelength and the microscope can therefore do what?

A

The electron beam has a very short wavelength and the microscope can therefore resolve objects well - it has a high resolving power

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4
Q

Light microscopes have poor resolution as a result of the relatively long wavelength of light.
In the 1930s however, a microscope was developed that used a beam of electrons instead of light.
An electron microscope has 2 main advantages:
1. The electron beam has a very short wavelength and the microscope can therefore resolve objects well - it has a high resolving power.
2. As electrons are negatively charged, the beam can be what?

A

As electrons are negatively charged, the beam can be focused using electromagnets

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5
Q

The best modern electron microscopes can do what?

A

The best modern electron microscopes can resolve objects that are just 0.1 nm apart

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6
Q

The best modern electron microscopes can resolve objects that are just 0.1 nm apart, how many times better than a light microscope?

A

The best modern electron microscopes can resolve objects that are just 0.1 nm apart, 2,000 times better than a light microscope

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7
Q

Electrons are what by the molecules in air?

A 
Electrons are:
1. Absorbed
Or,
2. Deflected by
the molecules in air
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8
Q

The best modern electron microscopes can resolve objects that are just 0.1 nm apart, 2,000 times better than a light microscope.
Because electrons are absorbed, or deflected by the molecules in air, what has to happen in order for it to work effectively?

A 
Electrons are:
1. Absorbed
Or,
2. Deflected by
the molecules in air, a near-vacuum has to be created within the chamber of an electron microscope in order for it to work effectively
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9
Q

How many types of electron microscopes are there?

A

There are 2 types of electron microscopes, the:

  1. Transmission electron microscope (TEM)
  2. Scanning electron microscope (SEM)
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10
Q

The greater resolving power of an electron microscope compared to a light microscope is due to what?

A

The greater resolving power of an electron microscope compared to a light microscope is due to the electron beam having a shorter wavelength than light

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11
Q

The transmission electron microscope (TEM) consists of what?

A

The transmission electron microscope (TEM) consists of an electron gun that produces a beam of electrons

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12
Q

The transmission electron microscope (TEM) consists of an electron gun that produces a beam of electrons that is what?

A

The transmission electron microscope (TEM) consists of an electron gun that produces a beam of electrons that is focused onto the specimen by a condenser electromagnet

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13
Q

The transmission electron microscope (TEM) consists of an electron gun that produces a beam of electrons that is focused onto the specimen by a condenser electromagnet.
In a transmission electron microscope (TEM), the beam passes through what?

A

In a transmission electron microscope (TEM), the beam passes through a thin section of the specimen

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14
Q

The transmission electron microscope (TEM) consists of an electron gun that produces a beam of electrons that is focused onto the specimen by a condenser electromagnet.
In a transmission electron microscope (TEM), the beam passes through a thin section of the specimen.
Parts of this specimen do what?

A

Parts of this specimen:

  1. Absorb electrons
  2. Therefore appear dark
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15
Q

The transmission electron microscope (TEM) consists of an electron gun that produces a beam of electrons that is focused onto the specimen by a condenser electromagnet.
In a transmission electron microscope (TEM), the beam passes through a thin section of the specimen.
Parts of this specimen absorb electrons and therefore appear dark.
Other parts of the specimen do what?

A

Other parts of the specimen:

  1. Allow the electrons to pass through
  2. So appear bright
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16
Q

The transmission electron microscope (TEM) consists of an electron gun that produces a beam of electrons that is focused onto the specimen by a condenser electromagnet.
In a transmission electron microscope (TEM), the beam passes through a thin section of the specimen.
Parts of this specimen absorb electrons and therefore appear dark.
Other parts of the specimen allow the electrons to pass through and so appear bright.
An image is produced where?

A

An image is produced on a screen

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17
Q

The transmission electron microscope (TEM) consists of an electron gun that produces a beam of electrons that is focused onto the specimen by a condenser electromagnet.
In a transmission electron microscope (TEM), the beam passes through a thin section of the specimen.
Parts of this specimen absorb electrons and therefore appear dark.
Other parts of the specimen allow the electrons to pass through and so appear bright.
An image is produced on a screen and this can be what to give what?

A

An image is produced on a screen and this can be photographed to give a photomicrograph

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18
Q

The transmission electron microscope (TEM) consists of an electron gun that produces a beam of electrons that is focused onto the specimen by a condenser electromagnet.
In a transmission electron microscope (TEM), the beam passes through a thin section of the specimen.
Parts of this specimen absorb electrons and therefore appear dark.
Other parts of the specimen allow the electrons to pass through and so appear bright.
An image is produced on a screen and this can be photographed to give a photomicrograph.
The resolving power of the transmission electron microscope (TEM) is what?

A

The resolving power of the transmission electron microscope (TEM) is 0.1 nm

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19
Q

The transmission electron microscope (TEM) consists of an electron gun that produces a beam of electrons that is focused onto the specimen by a condenser electromagnet.
The resolving power of the transmission electron microscope (TEM) is 0.1 nm, but this can not always be achieved in practice, because what limit the resolution that can be achieved?

A

The resolving power of the transmission electron microscope (TEM) is 0.1 nm, but this can not always be achieved in practice, because difficulties preparing the specimen limit the resolution that can be achieved

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20
Q

The transmission electron microscope (TEM) consists of an electron gun that produces a beam of electrons that is focused onto the specimen by a condenser electromagnet.
The resolving power of the transmission electron microscope (TEM) is 0.1 nm, but this can not always be achieved in practice, because what is required?

A

The resolving power of the transmission electron microscope (TEM) is 0.1 nm, but this can not always be achieved in practice, because a higher energy electron beam is required

21
Q

The transmission electron microscope (TEM) consists of an electron gun that produces a beam of electrons that is focused onto the specimen by a condenser electromagnet.
The resolving power of the transmission electron microscope (TEM) is 0.1 nm, but this can not always be achieved in practice, because a higher energy electron beam is required and this may do what?

A

The resolving power of the transmission electron microscope (TEM) is 0.1 nm, but this can not always be achieved in practice, because:

  1. A higher energy electron beam is required
  2. This may destroy the specimen
22
Q

The transmission electron microscope (TEM) consists of an electron gun that produces a beam of electrons that is focused onto the specimen by a condenser electromagnet.
The main limitations of the transmission electron microscope (TEM) are that:
1. The whole system must be what?

A

The main limitations of the transmission electron microscope (TEM) are that the whole system must be in a vacuum

23
Q

The transmission electron microscope (TEM) consists of an electron gun that produces a beam of electrons that is focused onto the specimen by a condenser electromagnet.
The main limitations of the transmission electron microscope (TEM) are that:
1. The whole system must be in a vacuum and therefore what?

A

The main limitations of the transmission electron microscope (TEM) are that:

  1. The whole system must be in a vacuum
  2. Therefore living specimens cannot be observed
24
Q

The transmission electron microscope (TEM) consists of an electron gun that produces a beam of electrons that is focused onto the specimen by a condenser electromagnet.
The main limitations of the transmission electron microscope (TEM) are that:
1. The whole system must be in a vacuum and therefore living specimens cannot be observed.
2. What is required?

A

The main limitations of the transmission electron microscope (TEM) are that a complex ‘staining’ process is required

25
Q

The transmission electron microscope (TEM) consists of an electron gun that produces a beam of electrons that is focused onto the specimen by a condenser electromagnet.
The main limitations of the transmission electron microscope (TEM) are that:
1. The whole system must be in a vacuum and therefore living specimens cannot be observed.
2. A complex ‘staining’ process is required and even then the image is what?

A

The main limitations of the transmission electron microscope (TEM) are that:

  1. A complex ‘staining’ process is required
  2. Even then the image is not in colour
26
Q

The transmission electron microscope (TEM) consists of an electron gun that produces a beam of electrons that is focused onto the specimen by a condenser electromagnet.
The main limitations of the transmission electron microscope (TEM) are that:
1. The whole system must be in a vacuum and therefore living specimens cannot be observed.
2. A complex ‘staining’ process is required and even then the image is not in colour.
3. The specimen must be what?

A

The main limitations of the transmission electron microscope (TEM) are that the specimen must be extremely thin

27
Q

The transmission electron microscope (TEM) consists of an electron gun that produces a beam of electrons that is focused onto the specimen by a condenser electromagnet.
The main limitations of the transmission electron microscope (TEM) are that:
1. The whole system must be in a vacuum and therefore living specimens cannot be observed.
2. A complex ‘staining’ process is required and even then the image is not in colour.
3. The specimen must be extremely thin.
4. The image may what?

A

The main limitations of the transmission electron microscope (TEM) are that the image may contain artefacts

28
Q

The transmission electron microscope (TEM) consists of an electron gun that produces a beam of electrons that is focused onto the specimen by a condenser electromagnet.
The main limitations of the transmission electron microscope (TEM) are that:
1. The whole system must be in a vacuum and therefore living specimens cannot be observed.
2. A complex ‘staining’ process is required and even then the image is not in colour.
3. The specimen must be extremely thin.
4. The image may contain artefacts.
Artefacts are what?

A

Artefacts are things that result from the way the specimen is prepared

29
Q

The transmission electron microscope (TEM) consists of an electron gun that produces a beam of electrons that is focused onto the specimen by a condenser electromagnet.
The main limitations of the transmission electron microscope (TEM) are that:
1. The whole system must be in a vacuum and therefore living specimens cannot be observed.
2. A complex ‘staining’ process is required and even then the image is not in colour.
3. The specimen must be extremely thin.
4. The image may contain artefacts.
Artefacts are things that result from the way the specimen is prepared.
Artefacts may appear where?

A

Artefacts may appear on the finished photomicrograph, but are not part of the natural specimen

30
Q

The transmission electron microscope (TEM) consists of an electron gun that produces a beam of electrons that is focused onto the specimen by a condenser electromagnet.
The main limitations of the transmission electron microscope (TEM) are that:
1. The whole system must be in a vacuum and therefore living specimens cannot be observed.
2. A complex ‘staining’ process is required and even then the image is not in colour.
3. The specimen must be extremely thin.
4. The image may contain artefacts.
Artefacts are things that result from the way the specimen is prepared.
Artefacts may appear on the finished photomicrograph, but are not part of the natural specimen.
It is therefore not always easy to be sure that what?

A

It is therefore not always easy to be sure that what we see on a photomicrograph really exists in that form

31
Q

In the transmission electron microscope (TEM), the specimens must be extremely thin to allow what?

A

In the transmission electron microscope (TEM), the specimens must be extremely thin to allow electrons to penetrate

32
Q

In the transmission electron microscope (TEM), the specimens must be extremely thin to allow electrons to penetrate.
The result is therefore what?

A

The result is therefore a:
1. Flat
2. 2D
image

33
Q

In the transmission electron microscope (TEM), the specimens must be extremely thin to allow electrons to penetrate.
The result is therefore a flat, 2D image.
We can partly get over this by doing what?

A

We can partly get over this by taking a series of sections through a specimen

34
Q

In the transmission electron microscope (TEM), the specimens must be extremely thin to allow electrons to penetrate.
The result is therefore a flat, 2D image.
We can partly get over this by taking a series of sections through a specimen.
We can then do what?

A

We can then build up a 3D image of the specimen

35
Q

In the transmission electron microscope (TEM), the specimens must be extremely thin to allow electrons to penetrate.
The result is therefore a flat, 2D image.
We can partly get over this by taking a series of sections through a specimen.
We can then build up a 3D image of the specimen by doing what?

A

We can then build up a 3D image of the specimen by looking at the series of photomicrographs produced

36
Q

In the transmission electron microscope (TEM), the specimens must be extremely thin to allow electrons to penetrate.
The result is therefore a flat, 2D image.
We can partly get over this by taking a series of sections through a specimen.
We can then build up a 3D image of the specimen by looking at the series of photomicrographs produced.
However, this is a what process?

A

This is a:
1. Slow
2. Complicated
process

37
Q

In the transmission electron microscope (TEM), the specimens must be extremely thin to allow electrons to penetrate.
The result is therefore a flat, 2D image.
We can partly get over this by taking a series of sections through a specimen.
We can then build up a 3D image of the specimen by looking at the series of photomicrographs produced.
However, this is a slow and complicated process.
One way in which this problem has been overcome is what?

A

One way in which this problem has been overcome is the development of the scanning electron microscope (SEM)

38
Q

All the limitations of the transmission electron microscope (TEM) also apply to the scanning electron microscope (SEM), except that what?

A

All the limitations of the transmission electron microscope (TEM) also apply to the scanning electron microscope (SEM), except that specimens need not to be extremely thin

39
Q

All the limitations of the transmission electron microscope (TEM) also apply to the scanning electron microscope (SEM), except that specimens need not to be extremely thin, because what?

A

All the limitations of the transmission electron microscope (TEM) also apply to the scanning electron microscope (SEM), except that specimens need not to be extremely thin, because electrons do not penetrate

40
Q

All the limitations of the transmission electron microscope (TEM) also apply to the scanning electron microscope (SEM), except that specimens need not to be extremely thin, because electrons do not penetrate.
Similar to a transmission electron microscope (TEM), the scanning electron microscope (SEM) does what?

A

Similar to a transmission electron microscope (TEM), the scanning electron microscope (SEM) directs a beam of electrons on to the surface of the specimen from above

41
Q

All the limitations of the transmission electron microscope (TEM) also apply to the scanning electron microscope (SEM), except that specimens need not to be extremely thin, because electrons do not penetrate.
Similar to a transmission electron microscope (TEM), the scanning electron microscope (SEM) directs a beam of electrons on to the surface of the specimen from above, rather than doing what?

A

Similar to a transmission electron microscope (TEM), the scanning electron microscope (SEM) directs a beam of electrons on to the surface of the specimen from above, rather than penetrating it from below

42
Q

All the limitations of the transmission electron microscope (TEM) also apply to the scanning electron microscope (SEM), except that specimens need not to be extremely thin, because electrons do not penetrate.
Similar to a transmission electron microscope (TEM), the scanning electron microscope (SEM) directs a beam of electrons on to the surface of the specimen from above, rather than penetrating it from below.
The beam is then what?

A

The beam is then passed:
1. Back
2. Forth
across a portion of the specimen in a regular pattern

43
Q

All the limitations of the transmission electron microscope (TEM) also apply to the scanning electron microscope (SEM), except that specimens need not to be extremely thin, because electrons do not penetrate.
Similar to a transmission electron microscope (TEM), the scanning electron microscope (SEM) directs a beam of electrons on to the surface of the specimen from above, rather than penetrating it from below.
The beam is then passed back and forth across a portion of the specimen in a regular pattern.
The electrons are what by the specimen?

A

The electrons are scattered by the specimen

44
Q

All the limitations of the transmission electron microscope (TEM) also apply to the scanning electron microscope (SEM), except that specimens need not to be extremely thin, because electrons do not penetrate.
Similar to a transmission electron microscope (TEM), the scanning electron microscope (SEM) directs a beam of electrons on to the surface of the specimen from above, rather than penetrating it from below.
The beam is then passed back and forth across a portion of the specimen in a regular pattern.
The electrons are scattered by the specimen and the pattern of this scattering depends on what?

A

The electrons are scattered by the specimen and the pattern of this scattering depends on the contours of the specimen surface

45
Q

All the limitations of the transmission electron microscope (TEM) also apply to the scanning electron microscope (SEM), except that specimens need not to be extremely thin, because electrons do not penetrate.
Similar to a transmission electron microscope (TEM), the scanning electron microscope (SEM) directs a beam of electrons on to the surface of the specimen from above, rather than penetrating it from below.
The beam is then passed back and forth across a portion of the specimen in a regular pattern.
The electrons are scattered by the specimen and the pattern of this scattering depends on the contours of the specimen surface.
We can build up a 3D image by what?

A

We can build up a 3D image by computer analysis of the pattern of:

  1. Scattered electrons
  2. Secondary electrons produced
46
Q

The basic scanning electron microscope (SEM) has a lower what than a transmission electron microscope (TEM)?

A

The basic scanning electron microscope (SEM) has a lower resolving power than a transmission electron microscope (TEM)

47
Q

The basic scanning electron microscope (SEM) has a lower resolving power than a transmission electron microscope (TEM), around what?

A

The basic scanning electron microscope (SEM) has a lower resolving power than a transmission electron microscope (TEM), around 20 nm

48
Q

The basic scanning electron microscope (SEM) has a lower resolving power than a transmission electron microscope (TEM), around 20 nm, but is still what than a light microscope?

A

The basic scanning electron microscope (SEM) has a lower resolving power than a transmission electron microscope (TEM), around 20 nm, but is still 10 times better than a light microscope

49
Q

The greater resolving power of an electron microscope compared to a light microscope is due to the electron beam having what?

A 
The greater resolving power of:
1. An electron microscope
compared to
2. A light microscope
is due to the electron beam having a shorter wavelength than light

AQA A Bio Unit 1 Biological Molecules (36 decks)

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