Microscopes

Question 1

Define the term ‘magnification’

Answer 1

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

Question 2

Define the term ‘organelles’

Answer 2

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

Question 3

Define the term ‘photomicrograph’

Answer 3

Photograph of an image seen using an optical microscope

Question 4

Define the term ‘resolution’

Answer 4

The ability to be able to distinguish between two points clearly
The clarity of an image

Question 5

Define the term ‘electron micrograph’

Answer 5

Photograph of an image seen using an electron microscope

Question 6

What type of magnification do microscopes produce?

Answer 6

Linear magnification

Question 7

List four reason as to why optical microscopes are still used in schools

Answer 7

cheap
easy to use
portable
used to study whole and living specimens

Question 8

Explain simply how optical microscopes work

Answer 8

They relay on lenses to focus a beam of light

Question 9

What is the maximum magnification of an optical microscope?

Answer 9

X1500

Question 10

Explain why list microscopes can not magnify any higher than around X1500 effectively

Answer 10

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

Question 11

What is the maximum resolution of optical microscopes?

Answer 11

200 nm

Question 12

What type of light does optical microscopes use?

Answer 12

Visible light

Question 13

What are the four types of microscopes?

Answer 13

Optical
Laser Scanning
Scanning Electron
Transmission Electron

Question 14

Explain why ribosomes cannot be seen using an optical microscope?

Answer 14

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

Question 15

Explain how to use light microscope

Answer 15

Place specimen onto the stage
Lens is placed over the specimen
Use the knob to focus the image while looking in the eyepiece
While viewing the image adjust the iris diaphragm for optimum light
Change the objectives X10 X40
Look at the specimen

Question 16

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

Answer 16

total magnification = objective lens magnifying power X magnifying power of the eyepiece lens

Question 17

How do modern digital microscopes display their image?

Answer 17

On a computer screen

Question 18

What is the alternative name for laser scanning microscope?

Answer 18

Confocal microscope

Question 19

Explain how laser scanning microscopes work

Answer 19

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

Question 20

The images produced by a laser scanning microscopes are high …. and show high…….

Answer 20

Resolution

Contrast

Question 21

Laser scanning microscopes have a special feature

what is it?

Answer 21

Depth selectivity

Question 22

Explain what depth selectivity is

Answer 22

It mean 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

Question 23

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

Answer 23

The medical profession and biological research

Question 24

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

Answer 24

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

Question 25

What are the two types of electron microscopes?

Answer 25

Transmission Electron | Scanning Electron

Question 26

What is the maximum resolution of a laser scanning microscope?

Answer 26

X2000

Question 27

Explain how an electron microscope works

Answer 27

They use a beam of fast travelling electrons that are fired from a cathode and focused by magnets

Question 28

Explain the types of images produced by electron microscopes?

Answer 28

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

Question 29

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

Answer 29

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

Question 30

Explain how transmission electron microscopes work

Answer 30

The beam of electrons shot by the cathode pass through the specimen and some of the electrons pass through and are focused onto the screen/photographic plate

Question 31

Explain the electron micrography that TEM's produce

Answer 31

They form a 2D black and white images

Question 32

What is the maximum magnification formed by TEM's?

Answer 32

X 2 million

Question 33

Explain how SEM microscopes work

Answer 33

The electron shot by the cathode don't pass through the specimen as the electrons bounce off and are focused on screen

Question 34

Explain the image that SEMS give

Answer 34

The images that re produced re black and white and are 3D | Computer software programmes can also ass false colour

Question 35

List three disadvantages that are with both types of electron microscopes

Answer 35

Very expensive Very large Need training and skill to be able to use them

Question 36

Specimens used for electron microscopes have t be .... when used in the microscopes

Answer 36

Dead

Question 37

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

Answer 37

They can be potentially hazardous for humans