Using a Microscope

Question 1

What is an eyepiece graticule?

Answer 1

A small disc that has an engraved ruler which can be placed into the eyepiece of a microscope to act as a ruler in the FOV.

Question 2

What is the use of a stage micrometer scale?

Answer 2

Used to find out how many micrometers each graticule unit represents.
Since a graticule has no fixed unit, it must be calibrated for the objective lens that is in use. By using the two scales together, the number of micrometers each graticule unit is worth can be worked out.

Question 3

What are stains used for?

Answer 3

Makes tissue appear coloured/visible

Question 4

How do dyes work?

Answer 4

They use absorbed specific colours of light while reflecting others; making the structures within the specimen that have been absorbed by the dye visible

Question 5

What is differential staining?

Answer 5

Where certain specimens or sections are stained with multiple dyes to ensure the different tissues within the specimen show up.

Question 6

What are some common stains?

Answer 6

• toluidine blue (turns cells blue)
• phloroglucinol (turns cells red/pink)

Question 7

What type of electron microscope requires staining and why?

Answer 7

TEMs - specimen must be stained in order to absorb the electrons. As electrons have no colour - the dye stains the tissue making it different shades of grey.

Question 8

What are some common examples of dye for TEMs?1

Answer 8

• heavy metal compounds (they absorb electrons well)
• osmium tetroxide
• ruthenium tetroxide

Question 9

Is staining a natural process?

Answer 9

• Mostly not natural in photomicrographs (light microscopes), however chloroplasts have their own green pigment.
• Never natural in micrographs (electron), as colour added is using an image processing software