Microscopes

Question 1

Describe what is meant by the magnification of an object

Answer 1

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

Question 2

What is the material that is placed under a microscope called

Answer 2

• An object

Question 3

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

Answer 3

• An image

Question 4

What are the two types of microscopes called (GCSE)

Answer 4

• Optical microscope
• Electron microscope

Question 5

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

Answer 5

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

Question 6

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

Answer 6

• Resolution

Question 7

Why does increasing the magnification sometimes result in a blurry image

Answer 7

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

Question 8

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

Answer 8

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

Question 9

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

Answer 9

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

Question 10

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

Answer 10

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

Question 11

What is the radiation source for optical microscopes

Answer 11

Light

Question 12

What are the 2 lenses in a light microscope called

Answer 12

• Objective lens
• Eyepiece lens

Question 13

What is the maximum magnification in a light microscope

Answer 13

X1500

Question 14

How do you calculate the total magnification of an optical microscope

Answer 14

Eyepiece X objective

Question 15

What is the maximum resolution in a light microscope

Answer 15

200nm

Question 16

State the advantages of an optical microscope

Answer 16

• produce coloured images
• view live specimens
• portable

Question 17

Describe what happens in a transmission electron microscope

Answer 17

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

Question 18

What is the radiation source for transmission electron microscopes

Answer 18

Electrons

Question 19

Why do electron microscopes have a higher resolution than light

Answer 19

Shorter wavelength

Question 20

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

Answer 20

Denser parts absorb more electrons, therefore they appear darker

Question 21

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

Answer 21

Less dense parts transmit electrons

Question 22

Describe what happens in a scanning electron microscope

Answer 22

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

Question 23

State the advantages of electron microscopes (TEM & SEM)

Answer 23

• 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

Question 24

State the disadvantages of electron microscopes (TEM & SEM)

Answer 24

• 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

Question 25

What is the maximum magnification of a TEM and SEM

Answer 25

X 500,000

Question 26

What is the maximum resolution for a TEM

Answer 26

0.1nm

Question 27

What is the maximum resolution for a SEM

Answer 27

20nm

Question 28

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

Answer 28

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