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Cells > Microscopes > Flashcards

Microscopes Flashcards

1
Q

Describe what is meant by the magnification of an object

A
  • How many times bigger an image appears than it’s actual size
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2
Q

What is the material that is placed under a microscope called

A
  • An object
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3
Q

What is the appearance of the material when viewed under a microscope called

A
  • An image
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4
Q

What are the two types of microscopes called (GCSE)

A
  • Optical microscope
  • Electron microscope
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5
Q

Describe what is meant by the resolution/resolving power of a microscope

A
  • The minimum distance apart that two objects can appear as separate objects
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6
Q

The smallest organelle that can be viewed by a microscope is determined by:
A) Magnification
B) Resolution

A
  • Resolution
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7
Q

Why does increasing the magnification sometimes result in a blurry image

A
  • Beyond the limit of resolution, increasing the image further will result in the image looking blurry
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8
Q

Why can’t organelles like mitochondria be seen under an optical microscope

A
  • The mitochondria is too small and the resolving power (resolution) is too low
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9
Q

A student cannot see the organelles of a red blood cell, explain why

A

Red blood cell has no organelles because their cytoplasm is filled with hämoglobin

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10
Q

What are the 3 types of microscopes you need to know about at A-level

A
  • Optical microscope
  • Scanning electron microscope (3D image)
  • Transmission electron microscope (2D image)
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11
Q

What is the radiation source for optical microscopes

A

Light

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12
Q

What are the 2 lenses in a light microscope called

A
  • Objective lens
  • Eyepiece lens
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13
Q

What is the maximum magnification in a light microscope

A

X1500

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14
Q

How do you calculate the total magnification of an optical microscope

A

Eyepiece X objective

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15
Q

What is the maximum resolution in a light microscope

A

200nm

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16
Q

State the advantages of an optical microscope

A
  • produce coloured images
  • view live specimens
  • portable
17
Q

Describe what happens in a transmission electron microscope

A
  • Electrons pass through the thin specimen
  • Denser parts absorb more specimen
  • Therefore denser parts appear darker
18
Q

What is the radiation source for transmission electron microscopes

A

Electrons

19
Q

Why do electron microscopes have a higher resolution than light

A

Shorter wavelength

20
Q

What causes parts of the image to appear darker in transmission electron microscopes

A

Denser parts absorb more electrons, therefore they appear darker

21
Q

What causes parts of the image to appear lighter in a transmission electron microscope

A

Less dense parts transmit electrons

22
Q

Describe what happens in a scanning electron microscope

A
  • Electrons are scattered off the surface of the specimen, and so they produce a 3D image
23
Q

State the advantages of electron microscopes (TEM & SEM)

A
  • Scanning electron microscopes allows us to see 3D images
  • Transmission electron microscopes have the greatest resolving power (resolution), which allows us to see the smallest organelles
24
Q

State the disadvantages of electron microscopes (TEM & SEM)

A
  • The specimen must be dead as it’s placed in a vacuum
  • The specimen must be extremely thin and there is a complex staining process, which is time consuming to prepare
  • Artefacts: defects in images caused by errors in preparation, therefore it’s difficult to tell if they’re part of the real object or not
25
Q

What is the maximum magnification of a TEM and SEM

A

X 500,000

26
Q

What is the maximum resolution for a TEM

A

0.1nm

27
Q

What is the maximum resolution for a SEM

A

20nm

28
Q

Explain why some organelles could be
seen with a transmission electron microscope
but not with an optical microscope.

A

An electron microscope has a higher resolution; as electrons have a shorter wavelength.

29
Q
A

Cells (25 decks)

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