Lab 3: Microscopes

Magnification

Makes things appear
larger

Resolution

The ability of an optical instrument to distinguish two points that are close together as separate points

Contrast

The difference between the lightest and the darkest parts of an image.

Stains

_________ are often used to improve contrast.

Types of microscopes:

1. compound light microscope

2. dissecting microscope

Field of View:

the portion of the slide you can view at any given magnification

As magnification increases, ____________ decreases and brightness decreases.

field of view

Knowing the _______ of the field of view can help estimate length of views specimen/structures.

size

Only use ___________ when focusing with the scanning objective lens

course-adjustment knob

Use ___________________ when focusing with the low power objective lens and high-power objective lens.

fine-adjustment knob

As you move up in power the field of view gets ____________

smaller

Begin with the stage as far down as possible, using __________________.

scanning objective lens

Parfocal lenses:

a lens that stays in focus when magnification/focal length is changed.

Ocular is always:

10x

scanning -

RED 40x > x4

low power objective -

YELLOW 100x > x10

High power objective -

BLUE 400x > x40

Oil immersion-

WHITE OR BLACK; Must use oil

1000x > x100

Putting a microscope away:

1. lower the stage

2. remove the slide

3. put the scanning objective into place

4. turn off microscope

5. wrap cord properly

6. use two hands to put it back into the cabinet

Which types of specimens would you use a stereoscope (dissecting) to observe?

• plants

• insects

• small specimens

• rocks

. Explain why it is necessary to calibrate the ocular micrometer for each objective lens:

without doing so, measurements will be inaccurate.