2.1.1- Microscopes Flashcards

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1
Q

Define the term ‘magnification’.

A

The number of times larger an image appears, compared to the size of the original object.

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2
Q

Define the term ‘organelles’.

A

Small structures that are within cells- each of which has a specific function.

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3
Q

Define ‘photomicrograph’.

A

Photograph of an image seen using an optical microscope.

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4
Q

What is ‘resolution’?

A

The ability to be able to distinguish between two points clearly.

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5
Q

Microscopes produce what kind of magnification?

A

Linear magnification.

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6
Q

List four reasons as to why optical (aka light) microscopes are still used in schools, colleges and labs.

A
  • relatively cheap
  • relatively easy to use
  • can be used to study WHOLE AND LIVING SPECIMENS
  • portable- can be used in the field and lab
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7
Q

Explain simply how optical microscopes work.

A

They rely on lenses to focus a beam of light.

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8
Q

What is the maximum magnification of an optical microscope?

A

X1500

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9
Q

Explain why light microscopes can not magnify any higher than around x1500 effectively.

A

As their resolution is limited- they cannot magnify any higher whilst also producing clear images.

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10
Q

What is the maximum resolution of optical microscopes?

A

200 nanometers.

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11
Q

What are the four types of microscopes?

A
  • Optical microscope
  • Laser scanning microscope
  • Scanning electron microscope
  • Transmission electron microscope
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12
Q

Explain why ribosomes cannot be seen using an optical microscope.

A

They are about 20nm diameter so are smaller than the resolution of the optical microscope (200nm)

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13
Q

What is the formula for calculating the total magnifying power of an optical microscope?

A

Total magnification= objective lens magnifying power ‘X’ magnifying power of eyepiece lens

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14
Q

Define the term ‘electron micrograph’.

A

Photograph of an image that is seen using an electron microscope.

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15
Q

How do modern digital microscopes display their image?

A

On computer screen.

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16
Q

What is the alternative name for laser scanning microscopes?

A

Confocal microscopes.

17
Q

Explain how laser scanning microscopes work.

A

They use laser light to scan an object point by point and assemble the pixel information by computer, on a computer screen.

18
Q

The images produced by laser scanning microscopes are high _________ and show high __________.

A

High resolution.

High contrast.

19
Q

Laser scanning microscopes have a special feature. What is that?

A

Depth selectivity.

20
Q

Explain what depth selectivity is- a feature of laser scanning microscopes.

A

It means they can focus on structures at different depths within a specimen. It makes it useful to observe full and living specimens, as well as cells.

21
Q

What are the two main places where laser scanning microscopes are used?

A

The medical profession and biological research.

22
Q

Describe an example of how laser scanning microscopes are used in the medical profession.

A

They’re used to observe fungal filaments in the cornea of the eye of a patient with a fungal corneal infection. This gives a swift diagnosis- therefore, giving a more effective treatment.

23
Q

What are the two different types of electron microscopes.

A
  • Transmission electron microscopes.

* Scanning electron microscopes.

24
Q

What is the maximum resolution of a laser scanning microscope?

A

x2000

25
Q

Explain how electron microscopes work.

A

They use a beam of fast travelling electrons (wavelength about 0.004nm) that are fired from a cathode and focused, by magnets.

26
Q

Explain the types of images produced by electron microscopes.

A

They give clear and highly magnified images, especially compared to optical microscopes.

27
Q

In preparation for use by a TEM microscope, explain what has to happen to the specimen in preparation.

A

The specimen has to be chemically fixed by being dehydrated and stained.

28
Q

Explain how transmission electron microscopes work.

A

The beam of electrons shot by the cathode pass through the specimen (that’s stained with metal salts) and some of the electrons pass through and are focused onto the screen/ photographic plate.

29
Q

Explain the electron micrograph that TEM’s produce.

A

They form 2D black and white images.

30
Q

What is the maximum magnification formed by TEM’s.

A

x2million.

31
Q

Explain how the specimen for SEM microscopes must be prepared.

A

The electrons shot by the cathode don’t pass through the specimen (which is whole) as the electrons bounce off and are focused on the screen.

32
Q

Explain the image that SEM’s give.

A

The images produced are black and white and are 3D. Computer software programmes can also add false colour.

33
Q

List three disadvantages that are with both types of electron microscopes.

A

> very large.
very expensive.
need a great deal of skill and training to use.

34
Q

Specimens used for electron microscopes have to be _____ when used in the microscopes.

A

Dead.

35
Q

What are the effects the metallic salt stains used for staining can have on humans?

A

They can be potentially hazardous for humans.