microscopy

Question 1

Magnification =

Answer 1

Image size
——-———
Actual size

Question 2

Magnification

Answer 2

How enlarged an image is

Question 3

Resolution

Answer 3

How well you can distinguish two separate points to see in detail

Question 4

Resolution: light-TEM-SEM

Answer 4

200nm-0.2nm-2nm

Question 5

which microscope has the best resolution

Answer 5

TEM

Question 6

Magnification light-TEM-SEM

Answer 6

1500-1,000,000-500,00

Question 7

How does a light/optical microscope work?

Answer 7

Light passes from the condenser lens and through the specimen where certain wavelengths are filtered to produce an image. then light passes through the objective lens then eyepiece where magnification can be altered to be seen

Question 8

What are the advantages of light microscopes?

Answer 8

They are cheap.
You can observe living organisms.
You can produce a coloured or stained image.
It is easy to use.
It is small and portable.

Question 9

What are the advantages of electron microscopes?

Answer 9

More detail is seen because electrons have a smaller wavelength than light
They have a high magnification.
They have a higher resolution.

Question 10

How does a transmission electron microscope TEM work?

Answer 10

Uses electromagnets to force a beam of electrons transmitted through the specimen to produce 2-D images. Denser parts of the specimen absorb more electrons which makes them look darker.

Question 11

How does scanning electron microscope SEM work?

Answer 11

It Scans a beam of electrons across the surface of the specimen, this knocks of electrons from the specimen which are gathered in a cathode ray tube to form an image showing the surface of the specimen so it can be 3-D and has to be sliced to show the inside

Question 12

Why can electron microscopes not observe living organisms?

Answer 12

Microscope has to have a vacuum to ensure the electron beams travel in straight lines

Question 13

What are light microscopes used to observe?

Answer 13

Whole cells and tissues

Question 14

What are electron microscopes used to observe?

Answer 14

Organelles

Question 15

How can drawings be improved?

Answer 15

No shading
No overlapping
No arrowheads
Add a scale or magnification
Add a title

Question 16

How to make a sample for a light microscope

Answer 16

Place stain at the edge of sample
Lower covers slip at an angle using a mounted needle
Use blotting paper to remove excess stain
Use multiple stains to improve contrast

Question 17

Two different stains are used while making a slide to observe through a light microscope one stains the cytoplasm, one stains the nucleus, Why are they both needed?

Answer 17

Stain is needed for the cytoplasm for it to be visible against the background and a stain is needed for the nucleus to differentiate it from the cytoplasm

Question 18

How to view a sample through a light microscope

Answer 18

1. Select the lowest powered objective lens
2. Use the course adjustment knob to bring the stage up to just below the objective lens
3. Look down the eye piece and use the course adjustment knobs to move the stage down until image is roughly in focus
4. Adjust the focus with the fine adjustment knob until there is a clear image of the slide
5. If greater magnification was required, refocused the microscope using a higher powered objective lens

Question 19

What microscope would you use to observe the inside of a mitochondria and why 2 mark

Answer 19

An electron microscope because a high resolution and magnification is needed to study internal structures of mitochondria

Question 20

How to put a stain on a wet mount side

Answer 20

Put a drop of stain next to one edge of the covers sip and a piece of paper towel next to the opposite edge. The paper towel will draw the stain under the slip across the specimen.

Question 21

Safety precautions

Answer 21

Wear goggles/ gloves
take care not to break the glass
take care of the sharp tools

Question 22

Identify the microscope used to produce this image (blank and white and 2D)

Answer 22

Tem/ transmission electron microscope

Question 23

What is the difference between the images of light microscope and electron microscope

Answer 23

It has higher resolution so individual organelles can be observed better

Question 24

Which microscope has the best resolution and magnification

Answer 24

TEM

Question 25

How to measure the diameter of the nucleus of a cell using a light microscope

Answer 25

Use the eyepiece graticule and calibrate it by aligning two scales to find the length of one division
Measure the diameter using graticule units
And use to calculate actual diameter

Question 26

How can improvements be made to making a sample slide

Answer 26

Use a sharp blade to cut sample thin so individual cells can be observed
Choose a thinly sliced sample so maximum light penetrates sample
Squash slide to avoid air bubbles

Question 27

Benefits of using stains in microscopy

Answer 27

Higher contrast
Internal organelles more visible
So clearer image is observed

Question 28

Why is it important to use different stains when observing blood smear

Answer 28

To differentiate cells, organelles and have a higher contrast especially for white blood cells so they can be counted

Question 29

Examples of stains

Answer 29

Methylene blue
Giesma stain
Haematoxylin
Eosin

Question 30

What is a stage micrometre?

Answer 30

A microscope slide with an accurate scale that is used to work out the value of the divisions on the eye piece graticule at particular magnification

Question 31

What are scanning electron microscopes used to observe?

Answer 31

The surface of cells