Optical Microscopes

Question 1

What are the limitations of using an optical microscope

Answer 1

The size of cells or structures of tissues may appear inconsistent in different specimen slides​. Cell structures are 3D and the different tissue samples will have been cut at different planes resulting in inconsistencies when viewed on a 2D slide​
Optical microscopes do not have the same magnification power as other types of microscopes and so there are some structures that can not be seen​

Question 2

How can you use a graticule to take measurements of cells

Answer 2

Calibrate the graticule (in eye piece lens) using a stage micrometre. By using the two scales together the number of micrometres each graticule unit is worth can be worked out​
After this is known the graticule can be used as a ruler in the field of view​.

Question 3

How can you prevent a specimen your viewing from becoming dehydrated

Answer 3

Adding a drop of water to the specimen (beneath the coverslip) can prevent the cells from being damaged by dehydration​

Question 4

How do you prepare a liquid specimen on a microscope

Answer 4

Add a few drops of the sample to the slide using a pipette​. Cover the liquid/smear with a coverslip and gently press down to remove air bubbles​. Wear gloves to ensure there is no cross-contamination of foreign cells​

Question 5

How do optical microscopes work

Answer 5

Light is directed through the thin layer of biological material that is supported on a glass slide​
This light is focused through several lenses so that an image is visible through the eyepiece​
The magnifying power of the microscope can be increased by rotating the higher power objective lens into place​

Question 6

Why are optical microscopes an invaluable tool for scientists

Answer 6

They allow for tissues, cells and organelles to be seen and studied​. E.g. chromosomes in mitosis