Microscopy

Question 1

What do light microscopes use to form an image?

Answer 1

Light

Lenses

Question 2

What is the formula for magnification?

Answer 2

Magnification = Image Size/ Real Size

Question 3

What can be seen using a light microscope?

Answer 3

Individual cells and large sub-cellular structures like nuclei

Question 4

How do electron microscopes work?

Answer 4

Use electrons

Question 5

What can be seen using an electron microscope?

Answer 5

Internal structures of mitochondria and chloroplasts
Ribosomes
Chloroplasts

Question 6

What is the magnification of a light microscope?

Answer 6

X 2000

Question 7

What is the resolving power of a light microscope?

Answer 7

200 nm

Question 8

What is the magnification of an electron microscope?

Answer 8

X 2000 000

Question 9

What is the resolving power of an electron microscope?

Answer 9

0.2 nm

Question 10

What is resolution?

Answer 10

Ability to distinguish two points that are close together

Question 11

How does resolution affect the image?

Answer 11

Higher resolution gives a greater image

Question 12

Describe how you would prepare a microscope slide to view onion cells

Answer 12

Add a drop of water to the middle of a clean slide

Cut up an onion and separate it out into layers.

Use tweezers to peel off some epidermis tissue from the bottom of one of the layers

Using tweezers, place the epidermal tissue into the water on the slide

Add a drop of iodine solution

Place a cover slip on top. To do this, stand the cover slip upright on the slide next to the droplet of water, then carefully tilt and lower it so it covers the specimen. Try not to get any air bubbles in there

Question 13

How do you use a light microscope to look at the slide?

Answer 13

Clip the slide onto the stage

Select the lowest powered objective lens (lowest magnification)

Use the coarse adjustment knob to move the stage up to just below the objective lens

Look down the eyepiece. Use the coarse adjustment knob to move the stage downwards until the image is roughly in focus

Adjust the focus with the fine adjustment knob until you get a clear image of whats on the slide

If you need a greater magnification swap to a higher powered objective lens and refocus

Question 14

Describe how to draw observations from a microscope

Answer 14

Use pencil with a sharp point
Drawing should take up half the space available
Clear unbroken lines
No colours or shading
Subcellular structures drawn in proportion
Title
Magnification written
Label important features using straight uncrossed lines

Question 15

Why might you add a stain to a sample on a microscope slide?

Answer 15

The stain highlights objects in the cell by adding colour to them