Microscopy

Question 1

What is microscopy?

Answer 1

Microscopy is the science of investigating these small objects using a microscope.

Question 2

Microscopy has three important parameters: (3)

Answer 2

magnification, resolving power and contrast

Question 3

Early microscopes were called “simple” because they had only one lens and this limited the
magnification. What did the invention of the compound microscope result in?

Answer 3

The invention of the “compound” microscope advanced the study of microbiology, because the addition of more lenses increased the magnifying power.

Question 4

Today, there are numerous types of microscopes, such as the: (3)

Answer 4

• the simple stereo dissecting microscope
• the compound light microscope
• the transmission and scanning electron microscopes

Question 5

What is the function of the transmission and scanning electron microscopes?

Answer 5

Bombard specimens with electrons to build up images of the surface or thin sections of the
specimens.

Question 6

What is the function of simple dissecting microscopes?

Answer 6

Makes use of light that is reflected off the surface of a specimen.

Question 7

What is the function of the compound microscope?

Answer 7

Makes use of light that is transmitted through a specimen.

Question 8

A record of what is observed using a microscope is obtained using either drawings or
_______, which are photographs of images seen through a microscope.

Answer 8

micrographs

Question 9

Explain what is meant by the term “cross-section”.

Answer 9

A section made by a plane cutting anything transversely, especially at right angles to the longest axis.

Question 10

Explain what is meant by the term “longitudinal section”.

Answer 10

A section that is cut along the long axis of a structure. Longitudinal section is the opposite of a cross-section.

Question 11

The magnification obtained with the compound microscope depends on the magnifying
power of the _____ lens (usually x10) in combination with the ______. On a
compound microscope, there are usually four objective lenses, with magnifying powers of
___,___,___,___, respectively.

Answer 11

Ocular lens
Objective lens
x4, x10, x40 and x100

Question 12

Briefly explain how the light microscope works. (5)

Answer 12

1. Visible light is emitted from the light source
2. Condenser condenses light onto the specimen
3. Light passes through the specimen to the objective lens
4. Objective lens magnifies the image of the specimen with refraction
5. Ocular lens magnifies the image more and projects it to the eye.

Question 13

What advantages does the dissecting microscope have over the compound microscope? (4)

Answer 13

• Samples do not need to be sliced, and larger, live specimens can be observed.
• Light can be passed through from underneath the sample, but also from the top or side using an external light source.
• The lower magnification of the dissecting microscope gives the user a greater field of vision.
• Long working distance to enable easier dissection.

Question 14

What advantages does the compound microscope have over the dissecting microscope?

Answer 14

(i) High magnification is achieved since it uses two lenses instead of one.
(ii) It comes with its own light source.
(iii) It is relatively small in size; easy to use and simple to handle.
(iv) Limitations on the resolution by simple microscopes can be resolved by using compound microscopes.

Question 15

You need to calculate the _____ __ ______ (FOV) of your microscope. On low power, place a
clear ruler on the stage. Count the number of millimetre lines visible across the field
diameter.

Answer 15

field of view (FOV)

Question 16

What is the actual size formula?

Answer 16

𝑨𝒄𝒕𝒖𝒂𝒍 𝒔𝒊𝒛𝒆 𝒐𝒇 𝒔𝒑𝒆𝒄𝒊𝒎𝒆𝒏 = 𝑭𝑶𝑽 (μ𝒎) / 𝑵𝒖𝒎𝒃𝒆𝒓 𝒐𝒇 𝒕𝒊𝒎𝒆𝒔 𝒔𝒑𝒆𝒄𝒊𝒎𝒆𝒏 𝒇𝒊𝒕𝒔 𝑭𝑶𝑽

Question 17

What is the function of a stain?

Answer 17

The main reason you stain a specimen before putting it under the microscope is to get a better look at it, but staining does much more than simply highlight the outlines of cells. Some stains can penetrate cell walls and highlight cell components, and this can help scientists visualize metabolic processes.