Microscope Parts & Functions / Koehler Illumination

Question 1

The enhancement on the Imaging system will work less with what?

Answer 1

Dark stained chromosomes

Question 2

What are the the Kohler Illumination steps?

Answer 2

1-Center and focus the bulb.
2-Focus on the specimen with low power objective.
3-Close the field diaphragm completely.
4-Rack the condenser up or down until the field diaphragm edges are in focus.
5-Center the field diaphragm image.
6-Open the field diaphragm until the edges disappear.
7-Set the condenser diaphragm.

1-Place slide on the stage and bring to focus.
2-Stop down the Field Diaphragm.
3-Focus the Condenser
4-Open the Field Diaphragm to the edge of the field and center using the condenser centering controls.
5-Adjust the Condenser Aperture Diaphragm to about 2/3 of full open.

Question 3

Why do you use a coverslip for 100x oil objective?

Answer 3

To protect the specimen

Question 4

True or False? For bright field microscopy, the refractive index of crown glass, used in microscope lenses, is 1.515; therefore, mineral oil, with a refractive index of 1.460 would make suitable immersion oil.

Answer 4

False

Question 5

After the light source is centered, what is the next step in Kohler Illumination?

Answer 5

Close the field diaphragm

Question 6

How does a CCD create pixels?

Answer 6

Using a grid of photo cells that sense light intensity

Question 7

Various types of objectives can be used in the photographing of banded chromosomes. However, for optimal results objectives must correct for multiple wavelengths of light, curvature of field and have a high numerical aperture. If you were going to photograph a metaphase plate which of the following objectives would give the best result?

Answer 7

PlanApo 100/1.4 Oil 160/0.17

Question 8

When moving from 10x to 100x you notice the image is blurry. This is because?

Answer 8

There are 2 cover slips, or the slide is upside down.

Question 9

A tech looked at 10 different slides and printed different images for each. An artifact was found on each printed picture. What should be done?

Answer 9

Clean the printer.

Question 10

What affects resolution?

Answer 10

NA of objective
NA of condenser
Refractive Index of the mounting medium

Question 11

What is the thickness of the coverslip that can be used with the following labeled objective?
170/.17/oel/100/1.32

Answer 11

.17

Question 12

What is a phase microscope used for?

Answer 12

Accessing amniotic fluid confluency

Question 13

What is the function of the field diaphragm?

Answer 13

Controlling area of illumination

Question 14

For photomicrography of chromosomes, I want the best resolution possible, therefore I will always use:

Answer 14

An objective with a N.A. of 1.3 to 1.4

Question 15

Why cells cannot be observed under 100 x objective lens when slide is upside down?

Answer 15

In very short working distance, if the thickness of the cover glass exceeds the working distance then it is impossible to focus on the object.

Question 16

What is the function of condenser diaphragm?

Answer 16

Condenser diaphragm regulates resolution, contrast and depth of field; it is responsible for controlling the angle of the illuminating light cone (open increases the angle, closed decreases the angle).

Question 17

What is the difference between closing the condenser diaphragm and opening it?

Answer 17

When the condenser diaphragm is closed, the depth of field and contrast increase and the image will lose resolution and becomes darker. When opened, then the depth of field and resolution increase and the image will lose contrast and becomes darker.

Question 18

What is the purpose to use green filter in cytogenetic lab?

Answer 18

A green filter increases band contrast, and when observing Giemsa stained chromosomes a green filter is recommended.

Question 19

Why is immersion oil needed when technologist analyze metaphases with 100x objective lens?

Answer 19

Immersion oil is needed for better resolution and brightness and will produce a sharper and brighter image of the metaphase. The oil also eliminates any air gaps and loss of light due to refraction (bending of the light). This is because immersion oil also has the same refractive index of glass.

Question 20

What is the purpose of Kohler Illumination?

Answer 20

Producing even illumination of the specimen using small uneven light sources.

Question 21

True or False? Opening the condenser aperture diaphragm up completely will ensure the best resolution.

Answer 21

True

Question 22

How do you best describe the process of Koehler illumination?

Answer 22

The process of centering the light source and spreading the light uniformly over the field of view.

Question 23

After Koehler illumination has been set and the edge of light circle have been focused what other microscope part should be adjusted to ensure that there is a good contrast between the dark and light bands of the chromosome?

Answer 23

The condenser diaphragm should be closed down by 1/4 to 1/3.

Question 24

What are Brightfield Microscopes used for?

Answer 24

To view stained cells and chromosomes.

Question 25

What are Phase contrast microscopes used for?

Answer 25

To view cells and chromosomes without staining. / Inverted - To view live cell cultures.

Question 26

What are the 3 Fundamental Parameters of image quality?

Answer 26

Magnification
Resolution
Contrast