The microscope 1st year Topic 13

Question 1

Why is a microscope used?

Answer 1

To view objects or cell structures, or any small structures which are invisible to our naked eyes.

Microscopes make objects appear larger than they actually are

Question 2

Name the 2 types of microscopes

Answer 2

The light and the electron

Question 3

Why is the light microscope called a light microscope?

Answer 3

Because it uses visible light to view small objects

Question 4

What does magnifying an object mean?

Answer 4

To make an object appear larger than it actually is

Question 5

Therefore,why is the microscope used?

Answer 5

To magnify microscopic structures such as cells

Question 6

Up to how many times can a light microscope magnify?

Answer 6

1500 times

Question 7

What unit is used to view structures using a light microscope?

Answer 7

Micrometres (1 thousandth of a millimetre)

Question 8

What is a specimen?

Answer 8

A small sample of material

The object being looked at under the microscope

Question 9

What is the eye piece?

Answer 9

The part which you look true,it has a magnification of 10x

Helps to produce a magnified image

Question 10

What are the objective lenses?

Answer 10

There are 3 with 3 different magnifications: 10x,40x and 4x

Help to produce a magnified image

Question 11

What is added to the specimen just before placing it on the stage?

Answer 11

A glass slide with a cover slip is added to the specimen

Question 12

What is the stage?

Answer 12

Where the glass slide is placed/specimen

Question 13

What are the focusing knobs used for?

Answer 13

To focus the image.

There are 2 types; coarse focus knob and fine focus knob

Question 14

What is the mirror used for?

Answer 14

To reflect the sun’s light on the specimen

Question 15

Why does the stage has 2 stage clips?

Answer 15

They are used to hold the slide in place

Question 16

What is the iris diaphragm used for?

Answer 16

To control light intensity

Question 17

Define magnification

Answer 17

The number of times larger the image of an object is than the object itself

Question 18

How can we calculate the total magnification?

Answer 18

By multiplying the magnification of the objective lens by the magnification of the eye piece

Question 19

True or false.

Specimens can be seen using high or low power

Answer 19

True

Question 20

Organisms are usually too large or too small to be drawn on a piece of paper. Therefore how can we draw them?

Answer 20

We draw them to scale

Question 21

How do we calculate a scale?

Answer 21

Scale: drawing length divided by the actual length

Question 22

Therefore,what exactly is the scale?

Answer 22

The number of times larger your drawing is,than the specimen itself

Ex: specimen

2x (twice larger than the specimen itself)

or when it is smaller:

ex: 1/2

0.5x

Question 23

When is low and high power used?

Answer 23

Low power: only gives a general outline of the object

High power: when we wwant to see the details of an object

Question 24

What does an electron microscope use instead of light?

Answer 24

A beam of electrons which are focused by magnetic lenses

Electrons behave like waves, and they can be easily detected ,focused and produced

Question 25

Mention some differences between a light and an electron microscope

Answer 25

LIGHT: cheap
cheap to operate
small
magnifies up to 1500 times
Vacuum is not required
Images are in their natural colour

Electron: expensive
expensive to produce an electron beam
large and needs large rooms
magnify up to 500 000 times
Vacuum is required
Images are in black and white

Question 26

Just because the amount of lenses a microscope uses ,the magnification is higher but that doesn’t mean that a more detail can be seen.What does detail mainly depend on in a microscope

Answer 26

Resolving power

Question 27

Define resolving power

Answer 27

The smallest separation at which 2 objects can be distinguished

Question 28

What is staining?

Answer 28

Staining is used when different cellular structures need to be distinguished, since most cellular structures are transparent

Question 29

Mention 2 types of vital stains

Answer 29

Methylene blue which is suitable for nuclei.

Neutral red

Iodine solution which is suitable for starch

Question 30

True or false.

Increasing magnification will not increase the resolution further

Answer 30

True

The image is getting bigger but the ability to distinguish between 2 structures or more will not be noticeable

Question 31

True or false

The resolution of a light microscope is 5 nanometres

The resolution of an electron microscope is 0.2 micrometres

Answer 31

False

The opposite

Light microscope 0.2 micrometres
Therefore less than 0.2 micrometres will be seen as one object

Electron microscope: 5 nanometres

Question 32

Define resolution

Answer 32

The ability to separate 2 objects from each other

If 2 separate objects will NOT be resolved, they will be seen as one object

Question 33

Mention some advantages that an electron microscope has over a light microscope

Answer 33

A scanning electron microscope can view the specimen in 3D

Higher resolution and higher magnification

Higher depth of field