zoology lab 2

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created 6 years ago by Adunola_Bello
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updated 6 years ago by Adunola_Bello
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1

What are the steps for Koehler illumination?

1. Rotate 10x (yellow band) obective lens into the working position.

2. Lower the 10x objective using the coarse focus adjustment, then use fine focus adjestment to bring image to a sharp focus.

3. To correct eye focal differences, close left eye, and focus image using the focal adjustment knob. Now, close right eye and focus the image using the ring on the left eyepiece tube.

2

What does the Koehler illumination produce?

Centered, parallel rays of light that fall on the specimen.

3

What does the Koehler illumination give?

Best balance between maximum resolution and contrast of the image for a given objective.

4

How is Maximum contrast and depth of field achieved?

by adjusting the aperture diaphragm.

5

What does excessive illumination cause?

loss of contrast.

6

Always start microscopy on what power level?

low power

7

If you cannot find an object with a low power objective, will you find it under higher magnification?

No

8

Never use coarse focal control when...

Using high power magnification.

9

How is magnification accomplished?

by the interaction of the objective lens and the ocular lens.

10

What are the limiting factors for viewing small objects?

resolution of lens and contrast of the specimen.

11

the clarity of the image is referred to as...

resolution

12

The ability to discriminate two points as being separate is....

resolution

13

The Human eye has a resolution of....

100 um

14

The compound light microscope has a resolution of...

0.2 um

15

What is the Abbe formula?

R=0.61w/N.A

16

A number used in optics to describe the light collecting ability of a lens.

Numerical Aperture (N.A)

17

Describe the relationship between N.A and resolution

The larger the N.A, the better the resolution.

18

Describe the relationship between wavelength and resolution.

As the wavelength gets smaller, the resolution gets better.

19

If you can see a specimen on a microscope with your naked eye, it must me larger than..

100 um

20

The difference in brightness and color between the specimen and its surroundings.

Contrast

21

What is a common way to increase contrast in biological specimens?

to stain them with dyes.

22

What is Another way to enhance contrast?

Adjust diaphragm.

23

If you can see a specimen on a microscope with your naked eye, it must me larger than..

100 umq