Microscopy

Question 1

What do microscopes let us do?

Answer 1

Let us see things that we can’t see with the naked eye

Question 2

What are light microscopes?

Answer 2

1) They use light and lenses to form an image of a specimen and then magnify it
2) Let us see individual cells and large subcellular structures

Question 3

What are electron microscopes?

Answer 3

1) Use electrons instead of light to form an image
2) Higher magnification than light microscopes
3) Higher resolution (sharper image)
4) Let us see much smaller things in more detail (e.g mitochondria or chloroplasts.
5) Let us see tinier things like ribosomes and plasmids

Question 4

What is the formula for magnification?

Answer 4

Magnification = image size / real size

Question 5

How do you convert from micrometres (µm) to millimetres (mm)?

Answer 5

Divide by 1000

Question 6

Question:
A specimen is 50µm wide. Calculate the width of the image of the specimen under a magnification of x 100. Give the answer in mm.

Answer 6

Answer:
image size = magnification x real size
image size = 100 x 50
= 5000 µm
(5000 / 1000)
= 5 mm

Question 7

What is a microscope slide?

Answer 7

A strip of clear glass or plastic, which the specimen is mounted onto

Question 8

How would you prepare a slide to view onion cells?

Answer 8

1) Add a drop of water to the middle of a clean slide
2) Cut up an ion and separate it out into layers. Use tweezers to peel off some epidermal tissue from the bottom of one of the layers
3) Using the tweezers, place the epidermal tissue into the water on the slide
4) Add a drop of iodine solution. Iodine solution is a stain. Stains are used to highlight objects in a cell by adding colour to them
5) Place a cover slip on top. Try not to get any air bubbles under there.

Question 9

How do you use a light microscope?

Answer 9

1) Clip the slide you’ve prepared onto the stage
2) Select the lowest-powered objective lens
3) Use the coarse adjustment knob to move the stage up to just below the objective lens.
4) Look down the eyepiece. Use the coarse adjustment knob to move the stage downwards until the image is roughly in focus
5) Adjust the focus with the fine adjustment know, until you get a clear image of what’s on the slide
(If you need to see the slide with greater magnification, swap to a higher-powered objective lens and refocus)

Question 10

What do you do after looking through a microscope?

Answer 10

Draw your observations (neatly)